Tools that get the job done.
Tools organized by purpose. Convert units, analyze data, optimize results, or calculate on demand - each category groups tools by the work they do.
Budgeting
Budgeting tools for the money math that comes up between paydays: splitting a bill and tip across a table, dividing rent and shared costs among housemates, allocating a paycheck across needs, wants, and savings, and seeing what is actually left once the fixed costs are out. The arithmetic is simple. What makes it tedious is doing it on the spot, at the table or the start of the month, and getting the split exactly right so nobody is short.
Business
Business tools for the operational numbers a small business runs every week: average order value, customer acquisition cost, churn forecasting, SaaS plan break-even, margin and markup, hourly rate setting for service work, time-clock tracking, and invoice generation. The math is the standard textbook math; the value is in surfacing the inputs side-by-side so a comparison stays apples-to-apples and the levers that actually move the result are visible. The common misconception that costs the most money is conflating margin with markup; they sound similar but a 50% markup is only a 33% margin, and a 50% margin requires a 100% markup, which the margin and markup tools show side by side. A second common mistake is using gross AOV instead of AOV-net-of-discounts when comparing channels; the order-value tools surface both. If you are new to the category, start with the rate tools if you bill for your time (they work backward from your target take-home), the order-value and acquisition-cost tools together for any ecommerce business, and the invoicing tools for the actual document. The churn and break-even tools are the right starting point for subscription businesses that want a clear picture of their unit economics before raising or repricing. None of the tools require an account; the outputs are yours to copy or download.
Construction
Construction tools for the estimation work that comes before any project: square footage and material coverage, paint quantities accounting for primer and second coats, deck stain coverage adjusted for the roughness of the wood, and the unit conversions that recur on every job (inches to feet, square feet to square yards, cubic yards of concrete, board feet of lumber). The category is intentionally narrow and useful for a contractor on a tablet at the supply yard rather than a desktop estimating suite. The common mistake is using paint coverage figures from the can without adjusting for surface texture; bare drywall, primed drywall, smooth wood, and rough lumber all absorb paint at different rates, which is why the coverage tools here offer roughness modifiers rather than a single coverage number. If you are new to the category, start with the area tools for any room you are measuring (they handle rectangles, triangles, and circular sections in one form), the paint estimates before any indoor project, and the deck and stain coverage tools before any outdoor wood project. The tools cover residential and small commercial scales; structural load, code compliance, and engineering-grade design are out of scope and are not what these utilities are for. Confirm material orders against your supplier's spec sheet before purchase.
Cooking
Cooking tools for the math you actually run into in a kitchen: scaling a recipe up or down, swapping volume measurements for weight, adjusting for altitude, working out how many servings a cake yields, and substituting one ingredient for another in usable proportions. The arithmetic is rarely complicated. What makes it annoying is doing it in the middle of cooking, with a flour-covered phone and a recipe that lists tablespoons when your kitchen scale reads grams. The tools here are built to give the answer in one screen and remember your last inputs so the second halving of the recipe takes two seconds instead of a fresh hunt. The most common assumption that gets people in trouble is that one cup of any ingredient weighs the same; flour, sugar, oats, and shredded cheese are all different by a wide margin, which is why the cup-to-grams converters use per-ingredient densities rather than a single conversion factor. If you are new to the kitchen, start with the conversion tools for unit work, the serving calculators before any party where you have to feed a known number of guests, and the altitude adjustments if you live above about 3,000 feet and have been wondering why your cakes sink. Bakers should also look at Hydration Ratio and Baker's Percentage. The tools are usable from a phone in landscape with a wet finger.
Crypto & Blockchain
Crypto and blockchain tools for the two numbers that decide whether an on-chain activity is worth doing: what it costs and what it returns. The category covers mining profitability from hash rate, power draw, electricity price, and current network difficulty; trade profit and loss net of entry and exit fees; and transaction gas fees across Ethereum, Polygon, BSC, Arbitrum, Optimism, Avalanche, and Base, including the EIP-1559 base-fee-plus-tip model. Everything is an estimate from the inputs you supply, so the output is only as current as the price, hash rate, and gas figures you enter. The mistake that costs the most money is reading mining revenue as profit: a rig looks worthwhile at today's coin price until you subtract the electricity it burns around the clock and the next difficulty adjustment, both of which the mining tools here make you enter rather than assume. The second is treating a trade's headline gain as take-home while ignoring the fees on both sides, which the profit tools break out as their own line. If you are new to the category, start with the mining profitability tools before buying or running hardware, the profit tools to size a trade after fees, and the gas fee estimates before sending a transaction on a network where fees spike with congestion. None of these are live feeds or financial advice; confirm against a current block explorer or exchange before committing funds.
Data
Data tools for the reshape-and-clean work that sits between exporting from one system and importing into another: CSV to JSON for an API that wants structured input, JSON to CSV for an analyst who wants to open it in Excel, XML to CSV for legacy enterprise exports, CSV merging when a vendor splits the export by month, and Excel conversion for systems that only accept .xlsx. Everything runs in your browser, so files you process here are not uploaded to a server, which matters when the data contains anything you would rather not share. The common misconception is that CSV is a single, well-defined format; in practice every system disagrees about quoting, escaping, line endings, header presence, and how to encode embedded commas, which is why the converters here detect quoting style and offer overrides rather than assuming. If you are new to the category, start with the CSV and JSON converters when you need structured data for an API, the merge tools when you have a folder of similar exports that need to be combined, and the spreadsheet exports when the destination is a spreadsheet rather than another tool. The XML converters handle deeply nested input by flattening on a configurable path. None of these tools change your source file; they generate clean output and leave you to handle the originals.
Design
Design tools for color work, icon and asset preparation, depth-of-field math for photography that crosses into design, and the small format conversions that come up daily on a creative team. Color tools cover the standard formats (HEX, RGB, HSL, HSV, CMYK) with auto-detection on input so the converter does not need a manual mode switch, plus a color wheel that builds complementary, analogous, triadic, and split-complementary palettes from a chosen base. Icon and image utilities convert single images into multi-resolution ICO files and combine source PDFs into print-ready output. The common assumption that hurts brand work is that an RGB value and a CMYK value can be exact equivalents; they cannot, because the gamuts are different, which is why the color converters here show both an in-gamut approximation and a flag when the conversion would not survive a print run. If you are new to the category, start with the color pickers for any time you need to grab a color quickly, the harmony tools when you are building a palette from scratch, and the icon converters when a project needs a real Windows-format icon rather than a PNG renamed with the wrong extension. Photographers, designers shooting product, and anyone working with macro setups should look at the depth of field tools before a shoot, not after.
Development
Development tools for the small utilities that show up on every engineer's desktop and never feel important enough to install an app for: a strong password generator, a JSON validator and formatter with sane error messages, a JSON schema stripper for trimming a schema down to fit a model context window, a tokenizer for cost-estimating LLM prompts, a screen resolution simulator, a What-Is-My-IP analyzer, and a prompt chain tool for building multi-step model interactions. Everything runs client-side so the values you paste are not transmitted, which is the right answer for anything that contains keys, tokens, internal endpoints, or proprietary prompts. The common mistake when working with model context windows is counting words instead of tokens; the ratio differs by language and prompt style, and a long technical document can use 30 to 50 percent more tokens than its word count suggests, which is why the token tools here report per-model counts rather than a single average. If you are new to the category, start with the JSON validators for any malformed payload you need to debug, the credential generators for any new secret, and the token counters before sending a prompt that approaches a model's context limit. The prompt tools are the right place to start when you are decomposing a single large prompt into a more reliable multi-step sequence.
Drink
Drink tools for the proportions behind what ends up in the glass: scaling a recipe from a single serving to a full batch, balancing ingredients, dilution, and carbonation, and weighing a drink's nutrition, hydration, or strength against whether it is actually pleasant to drink. A beverage is mostly a ratio problem, water and flavor and whatever it is mixed or fortified with, and the work is holding those ratios steady when you change the serving size or chase a particular target.
Education
Education tools for the academic-administration math that students, parents, teachers, and advisors do every term: GPA across mixed credit systems, end-of-term grade projection from work already turned in, and what-if scenarios for the final exam (what grade do I need on the final to lock in a B). The GPA calculator handles the US 4.0 scale (with both 4.0 and 4.3 A+ policies), the International Baccalaureate scale, and primary and lower-secondary grading conventions. Honors and AP weighting is configurable because schools handle weighting differently and a single hard-coded rule would be wrong for a large fraction of students. The common misconception is that all credit hours weigh the same in a cumulative GPA; they do not, which is why the GPA tools here multiply grade points by credits before summing. If you are new to the category, start with the GPA tools at the end of each term to confirm what your transcript will show, and the grade projections mid-semester when you want to know what you need on remaining assignments to hit a target grade. The tools assume your school's scale matches one of the supported standards; if your institution uses a custom scale, the custom-scale mode is the right place to encode it.
Electronics
Electronics tools for the numbers that sit between a schematic and a working circuit: Ohm's law and the power equation solved from any two known values, resistor color bands decoded into resistance and tolerance with series and parallel combinations, PCB trace width, resistance, and impedance from the IPC-2221 tables and microstrip or stripline geometry, duty cycle and inductor and capacitor sizing for inverting buck-boost and forward converters, lumen, lux, and candela conversions for lighting, and what a device costs to run from its wattage, its hours, and your utility rate. Most of it is arithmetic anyone could do once by hand; the value is doing it forty times in an evening without a transcription error. The mistake that costs people boards is sizing a trace by habit instead of by copper weight and allowed temperature rise, which is why the trace-width tools here ask for both before reporting a width. If you are new to the category, start with the Ohm's law tools: they make the relationship between voltage, current, resistance, and power concrete, and every other tool here assumes it.
Encoding & Decoding
Encoding and decoding tools for the small format conversions that come up constantly in development, security work, and data plumbing: Base64 in both directions, URL-encoding and -decoding for query strings, text-to-binary for educational demonstrations, and the bidirectional flips that should take five seconds but somehow always take five minutes because the right CLI option is not in your shell history. Every tool runs in your browser, so the value you encode or decode is not transmitted; this matters for Base64-encoded secrets, OAuth state parameters, or anything you would not paste into a public web form. The common assumption that bites people is that URL-encoding and HTML-encoding are the same thing; they overlap but they are not interchangeable, which is why the URL tools here call out the specific spec they follow (RFC 3986) and handles the corner cases (plus signs in query strings, percent-encoded forward slashes in path segments) consistently. If you are new to the category, start with the Base64 tools for anything related to credentials, tokens, or data URIs; the URL encoders for any URL you are building programmatically; and the binary converters when you want to show a student or junior teammate how character encoding actually works at the byte level.
Entertainment
Entertainment tools for the calculations that are fun to run rather than strictly necessary: the kind of question you ask out of curiosity, then send to a friend. The category opens with planetary age conversion, which turns your Earth age or date of birth into the equivalent age you would be on every planet, dwarf planet, and major moon in the solar system, based on each body's orbital period. It is a quick way to feel how differently time passes across the solar system: a year on Mercury is 88 Earth days, so birthdays pile up fast, while a single Neptune year runs about 165 Earth years, meaning almost nobody has ever had one. The thing most people forget is that an age is not a fixed number but a count of orbits around one particular star, so on another planet you have completed a very different number of laps. If you are new to the category, there is one tool here for now, and it needs nothing but your birth date. The category is deliberately small and is expected to grow with more novelty and educational calculators; nothing here is meant to be taken as a serious measurement of anything.
Finance
Finance tools that compute the standard numbers you would otherwise build in a spreadsheet: loan and mortgage amortization, retirement projections with employer matching and inflation adjustment, APR back-calculated from fees, compound interest with arbitrary contribution patterns, payroll math, and the dozen smaller calculations that come up around buying a car, renting an apartment, or planning a budget. Every projection here uses standard time-value-of-money formulas with the assumptions stated on the tool page; there are no proprietary models or undisclosed fees baked into the numbers. The most common misconception is that an APR and an interest rate are the same thing. They are not: the APR reflects the true cost of borrowing including origination fees, points, and required insurance, and the difference between the two figures is exactly what the borrowing-cost tools here are designed to surface. A second common mistake is reading a 401(k) projection at face value without adjusting for inflation; the retirement projections here return both nominal and inflation-adjusted figures so the purchasing power of the final balance is visible alongside the headline number. If you are new to the category, start with the loan payment tools for any borrowing decision, the retirement projections before your next benefits enrollment, and the compound interest tools to understand how starting earlier with a smaller monthly contribution compares to starting later with a larger one. Tax estimates are general-purpose and not a substitute for a CPA.
Games
Games tools for the probability and randomness behind tabletop and card play: exact distributions for the sum of many dice, advantage and disadvantage on a single twenty-sided roll, percentile checks against a target, shuffled draws from a standard or jokered deck, printable bingo cards with a caller and win-pattern checks, lottery number sets drawn from the real game matrices, and Texas Hold'em equity against one to nine opponents. The dice tools here convolve one die at a time instead of fitting a normal curve, which is why a tail probability on the order of one in 10^22 is reported as a figure rather than rounded away to zero. The assumption that costs players the most is that a sum of dice behaves like one big die: two six-sided dice do not land on each total equally often, and a 7 arrives 16.67 percent of the time against 2.78 percent for a 12, which is the whole reason an exact distribution is worth having. If you are new to the category, start with the dice tools to see the shape of a sum, then the card and poker tools, which are careful to say which figures are counted exactly and which are sampled with a stated margin. Every random draw here comes from the browser's own pseudorandom generator, which is right for play and wrong for anything that has to be unpredictable.
Health
Health tools that compute the standard general-population estimates clinicians and coaches reach for: Body Mass Index against CDC adult and pediatric cutoffs, Basal Metabolic Rate using Mifflin-St Jeor, revised Harris-Benedict, or Katch-McArdle (the right choice depends on whether you know your body-fat percentage), total daily energy expenditure adjusted for activity level, macronutrient split for a given calorie target, sleep cycle timing, fertility windows, pregnancy due dates, and a blood alcohol estimate to help you decide when not to drive. Every result is an estimate, not a diagnosis, and the tools say so on the page; for anything that affects a real medical decision, the right answer is to talk to a clinician. The most common assumption that gets people in trouble is treating BMI as a fitness verdict; it is a population-level screening tool that does not distinguish lean mass from fat mass and routinely misclassifies muscular adults and the elderly, which is why the body composition tools here surface the caveats alongside the number. If you are new to the category, start with the body-mass and metabolic-rate tools together to establish baseline numbers, the calorie targets if you have a weight-change goal, and the sleep timing tools if you wake up groggy on a consistent schedule. The pregnancy and ovulation tools are written for general planning, not for clinical work.
Home & Garden
Home and garden tools for the practical numbers that come up before a project starts: lawn area for seeding, fertilizing, or estimating mowing time and cost, planting dates calibrated to your last frost, paint and stain coverage for indoor and outdoor surfaces, and the unit conversions that recur every season. The arithmetic is straightforward; the value is doing it once and getting the answer in the units you need for the bag, can, or seed packet rather than the units a textbook would prefer. The common mistake is buying seed or fertilizer by total area without subtracting beds, hardscape, and the strip the dog has worn bare; the lawn tools here accept obstruction inputs so the figure reflects the area you are actually treating. If you are new to the category, start with the lawn costing tools if you are quoting yard work or comparing service prices, and use the area tools under Construction when you need to convert a measured shape into something a bag or can label is calibrated against. The garden side of the category is still small and is expected to grow with planting-date calculators, soil amendment ratios, and irrigation schedule helpers. Send a request through the contact page for any seasonal calculation you keep running.
Marketing
Marketing tools for paid-acquisition and analytics math that media buyers and growth marketers run weekly: return on ad spend, target ROAS for a desired margin, total advertising cost of sale (tACoS) for marketplace sellers who care about organic-versus-paid mix, and the UTM-style URL construction that should be trivial but routinely produces broken links because somebody hand-edited a query string in a meeting. Everything runs in your browser so a campaign URL you are constructing is not sent to a server. The common misconception that wastes the most budget is treating ROAS and ROI as equivalent; ROAS is gross revenue divided by ad spend (a 4x ROAS can still be a money-losing campaign once costs are subtracted), while ROI accounts for cost of goods sold, fulfillment, and overhead. The return-on-ad-spend tools surface the difference and let you back-calculate the ROAS you actually need to hit a margin target. If you are new to the category, start with the return-on-ad-spend tools before any new campaign is set up, the order-value tools under Business for any ecommerce work, and a hand-built UTM URL only after you have run it through a URL encoder to make sure your special characters survive the trip. Channel-specific platforms publish their own reporting; these tools are for the math you do across them.
Materials
Materials tools for thickness, weight, and density conversion across the trade-specific units that workshops actually use: leather measured in ounces and irons, sheet metal in gauge numbers, lumber in nominal versus actual dimensions, and the metric or imperial equivalents you need when a supplier publishes only one of them. The arithmetic is straightforward; the value is having the conversion table memorized for you and surfacing the project context (what an 8-ounce leather is suitable for, what gauge a particular gauge number really represents) alongside the raw number. The most common misconception is that a 2x4 is actually two inches by four inches; nominal lumber dimensions are quite different from the actual planed sizes, which is the kind of thing that wrecks a project measured from a parts list rather than from the wood in your hand. If you are new to the category, start with the thickness converters if you work with leather goods, and bookmark the rest as you encounter them. The category is intentionally small and is expected to grow as we add tools for fabric weight, paper grammage, metal gauge, and the other unit systems that have not been added yet. Send a request through the contact page if there is a conversion you keep running into that we have not built.
Math
Math tools that compute the answers most often looked up in homework, lab notebooks, and back-of-envelope estimates: percentages, ratios, averages (arithmetic, geometric, harmonic) with the summary statistics that go with them, circle and triangle geometry, volumes for common solids, and fraction-decimal conversion with arbitrary repeating-decimal handling. The tools accept mixed input formats (fractions, decimals, percentages, mixed numbers) so you do not have to normalize before typing. Where multiple definitions exist (which mean to use, how to interpret a percentage change against a zero baseline), the tool surfaces the choice rather than guessing. The common misconception that creates the most wrong answers is confusing percentage-of with percentage-change; the percentage tools separate them into distinct modes for that reason. A second is using the arithmetic mean on data that is multiplicative (interest rates, growth factors, returns), where the geometric mean is the right answer, which is why the averaging tools return all three means side by side. If you are new to the category, start with the averaging tools for any dataset, the percentage tools for any pricing or ratio work, and the geometry tools for any homework involving radii and circumferences. The fraction converters handle the conversions kids run into in middle school and the ones engineers run into in tolerances.
Pets
Pet tools for the age conversions and life-stage estimates that help with routine care decisions: dog years to human years (size-aware, because a Chihuahua and a Great Dane age very differently), cat years to human years, and the equivalent for hamsters and other small companion animals. The point of the conversion is not the headline number; it is the implied veterinary care milestone (when senior screenings start, when dental cleanings should be on the schedule, when nutrition needs change). The common misconception is the old multiply-by-seven rule for dogs; it is wrong, especially for small and giant breeds, which mature and senesce at very different rates than mid-sized breeds. The tools here use size-category interpolation against published veterinary tables instead. If you are new to the category, start with the dog age tools and pick the size class that matches your dog's adult weight, then look at the cat equivalents for any cat over about seven years old, where the human-equivalent age starts changing fast. Separate tools handle the much shorter lifespan of pocket pets. These tools are general references; for anything that affects a real care decision, the right answer is to talk to a veterinarian who knows your animal.
Photography
Photography tools for the optical and timing math that should happen before the camera comes out: depth of field for a chosen sensor, lens, aperture, and subject distance; hyperfocal distance for landscape work; macro depth of field for product and insect photography; circle of confusion for unlisted sensor formats; aspect-ratio conversion for prints and crops; and interval timing for timelapse sequences. The formulas are standard optics; the value is in not having to look them up on a phone with cold hands at a viewpoint. The common assumption that wrecks shots is that depth of field depends only on aperture; sensor size, focal length, and subject distance all matter just as much, which is why the depth of field tools here ask for all four and report near limit, far limit, and the split between front and back sharpness rather than a single figure. If you are new to the category, start with the depth of field tools before any portrait or landscape shoot, the macro variants if you shoot close-up, and the circle of confusion tools if your camera body is not in the standard preset list. The tools assume a thin-lens approximation, which is accurate for normal subject distances and breaks down inside the macro range, where the macro-specific tool handles the correction.
Productivity
Productivity tools for the structured-thinking work that gets stuck without scaffolding: morphological matrices for systematic combinatorial idea generation, prompt chaining for breaking a single hard task into a more reliable sequence, and the smaller utilities that help when a problem is too vague to start. The category is intentionally narrow; we have deliberately not built a full project-management or task-tracking suite because the market is saturated with good options for that work. The common misconception is that brainstorming generates better ideas than structured methods; thirty years of creativity research consistently finds the opposite, which is why the matrix builders here exist as something to actually use rather than a concept to read about. If you are new to the category, start with the matrix builders when you are stuck on a design or strategy problem that has several semi-independent axes (target user x distribution channel x pricing model x packaging format, for example), and the prompt tools when a single prompt is producing inconsistent or wrong outputs from a model. Both tools work as scratch surfaces; they save state in your browser so you can leave and come back, and they export to plain text or JSON for sharing with a teammate.
SEO
SEO tools for the on-page work that an editor or content operator can finish without involving an engineer: title and meta description length checks, keyword density and prominence scoring, product listing optimization against marketplace character limits, and the small structural validations that catch the silly mistakes (no H1, duplicate H1s, missing alt text, an h-tag jump from h2 to h4). The work here is verification and tuning, not strategy. The common assumption to unlearn is that the meta description length is measured in characters; Google truncates by pixel width on the rendered SERP, which is why the length checkers here report both characters and pixel width and flag the latter as the binding constraint. A second common mistake is over-stuffing keywords; the keyword tools surface density, prominence, and co-occurrence, and the recommended ranges are conservative on purpose. If you are new to the category, start with the length checkers before any page goes live, the keyword tools when you are revising older content for a new target term, and the listing optimizers if you sell on Amazon, eBay, Etsy, or any marketplace that constrains your fields. None of the tools here promise rankings; they catch the on-page mistakes that would otherwise cost rankings.
Science
Science tools for the bench and field calculations that sit between a measurement and a usable number: radiocarbon age from the carbon 14 left in a sample, the decay law solved for any of its four unknowns, molar mass summed from a chemical formula, solution concentration moved between molarity, molality, mass percent, mole fraction, ppm and normality, primer melting and annealing temperatures by nearest-neighbor thermodynamics, mass flow rate across fourteen units, and dew point and wind chill from temperature with humidity or wind speed. Each tool names the published formula and the constants it uses, because in this domain a number without them is not a result. The mistake that quietly invalidates one is reading a reported figure as something it is not: radiocarbon ages are uncalibrated years before 1950 rather than calendar dates, and the two half-life conventions in use differ by about 3 percent, which is why both are reported side by side. If you are new to the category, start with the decay and dating tools if you need an age, the concentration and molar mass tools if you are making up a solution, and the atmospheric tools for comfort and frostbite thresholds, which carry the temperature and wind limits their source formulas are valid within.
Sports
Sports tools for the arithmetic that settles what a performance actually was: on-base percentage, slugging and OPS from a hit breakdown, a golf handicap index averaged from score differentials under the World Handicap System count table, and bicycle gear ratio, gear inches, development per crank revolution and road speed at a chosen cadence. These are published formulas rather than opinions, and the value is applying them consistently across a season of box scores or a drivetrain's worth of gear combinations. The detail that trips people up is which events belong in a denominator: a sacrifice fly counts against on-base percentage but not against batting average or slugging, so the three figures move independently and a player can gain in one while losing another. If you are new to the category, start with the batting tools if you are reading a box score, the handicap tools before entering a competition, and the drivetrain tools when choosing a chainring or cog, where wheel diameter comes from the bead seat diameter plus twice the tire width rather than the marketing size printed on the sidewall. None of this replaces an official ruling; soft and hard caps, for one, are left out of the handicap figure.
Technology
Technology tools for the device-and-display math that consumers and IT staff run into regularly: screen size and pixel density for choosing or comparing monitors and televisions, viewing-distance recommendations for a given resolution, aspect-ratio conversions for video work, and the small calculations around storage, bandwidth, and uptime. The category is heavier on consumer hardware than on enterprise infrastructure. The common misconception that costs people money is buying a screen by diagonal inches alone without checking pixel density; a 32-inch 4K display and a 32-inch 1080p display look very different at the same viewing distance, which is why the display tools here report PPI alongside the diagonal and the ideal viewing distance for the chosen resolution. If you are new to the category, start with the display tools before any monitor or television purchase, and pair them with the manufacturer's spec sheet rather than relying on retailer descriptions. The category will grow over time as we add tools for storage and bandwidth planning, which are the most commonly requested missing pieces. Send a request through the contact page if there is a calculation you keep running into.
Text
Text tools for the cleanup, measurement, and transformation work that writers, editors, developers, and content operators do dozens of times a day. Count words, characters, syllables, and reading time against a target. Normalize whitespace and line endings before pasting into a system that is fussy about them. Generate dummy text in your choice of flavor and length when designing a layout. Randomize lines for giveaways or A/B prompts. Remove invisible characters that were silently smuggled in by a copy-and-paste from a PDF. The most common assumption that bites people is that all whitespace is equivalent; non-breaking spaces, zero-width joiners, and various Unicode space characters look identical to a regular space on screen but break downstream tooling, exceed character limits invisibly, and trip up search and replace. The detection tools surface them; the whitespace formatters remove them in one pass. If you are new to the category, start with the counting tools for any writing task with a target length, the whitespace formatters before pasting into a system that has a character limit, and the placeholder generators when you are designing rather than writing. The Randomize Text Lines tool is the quiet favorite for anyone running a giveaway. The markdown formatters help when you are switching between editors that interpret markdown differently.
Time
Time tools for the date arithmetic that recurs constantly in planning and project management: days between two dates, workdays excluding weekends and holidays, countdowns to a deadline, time zone conversion, and the smaller calculations around overtime and time-and-a-half pay. Dates are easy to get wrong by one because of inclusive-versus-exclusive counting and time-zone boundaries, so the tools here state which convention they use and let you switch when the answer matters. The common assumption that causes the most trouble is that subtracting two timestamps gives you the right number of business days; weekends, public holidays, and partial start and end days all need to be handled explicitly, which is why the workday tools here take a holiday-list input and surface both the raw day count and the working-day count. If you are new to the category, start with the date-span tools for any general-purpose range (vacation length, project duration, age in days), the workday tools when you are planning around a deadline, and the time zone converters when you are coordinating with someone in a different region. The overtime tools handle the wage math for hourly workers and are the right place to verify a paycheck. Date math is one of the more error-prone corners of programming, which is why we standardized on a single underlying date library across the category.
Unit Conversion
Unit conversion tools for turning a measurement expressed in one unit into the same quantity in another, across every dimension that comes up in daily and technical work: length, area, volume, weight and mass, speed, pressure, power, torque, time, electrical units, and digital data, plus a general converter that spans all of them. Each converter carries a deep unit list rather than the handful most tools offer, with configurable decimal precision and support for fractions, mixed numbers, and scientific notation. The assumption that causes the most quiet errors is that a conversion is a single fixed factor. Digital storage has two competing standards, binary powers of 1024 and decimal powers of 1000, that disagree by a growing margin as the units get larger, which is why the storage converters here expose both rather than picking one silently. Volume and weight are not interchangeable without knowing the substance, since a cup of flour and a cup of water have different densities, which is why the volume-to-weight tools key on the material. If you are new to the category, start with the general converter for everyday work across dimensions, the storage converters for transfer figures where the binary-versus-decimal choice matters, and the volume-to-weight tools whenever a recipe or spec crosses between how much space something takes up and how much it weighs. These are arithmetic conversions using standard factors, not a metrology reference; for legal or trade measurement, confirm against the governing standard.
Video
Video tools for the technical math that sits between a creative decision and a finished file: aspect ratio conversion for cropping or letterboxing, frame-rate matching for footage shot at different speeds, resolution targets for a specific platform, and bitrate or storage estimates before a long shoot. The math is straightforward and the value is having the answer in one screen rather than juggling three reference sites and a calculator app. The common misconception worth unlearning is that frame rate and shutter speed are interchangeable; they are not, and the relationship between them (the 180-degree shutter rule for motion blur that looks natural) is what makes 24-frame-per-second footage look filmic and 60-frame-per-second footage with the same shutter look hyper-real. If you are new to the category, start with the aspect ratio tools before any crop or platform delivery, and use a manufacturer-published bitrate ladder rather than guessing when you are encoding for a specific service. The category is intentionally small and is expected to grow with color-space conversion, codec selection helpers, and storage planning tools for multi-camera shoots. Send a request through the contact page for any calculation you keep running and we will look at building it.
Web
Web tools for the small front-end work that interrupts a build: validating and formatting HTML, CSS, and JSON on the way into a CMS, converting pixel values to relative units for a responsive layout, and the structural checks that catch silly mistakes (missing alt text, deprecated tags, mismatched braces in stylesheet rules). The category is intentionally browser-only; nothing here requires installing a local build environment. The common misconception worth unlearning is that em and rem are interchangeable units; em compounds against the nearest font-size ancestor and rem is always relative to the root, which is why the unit converters here report both side by side and ask for the relevant root size only once. If you are new to the category, start with the markup validators on any handwritten code before publishing, and the unit converters the first time a layout needs to scale gracefully to large or small viewports. The category is small on purpose; the goal is to cover the cases that are common enough to need a tool but small enough that nobody wants a dedicated build pipeline for them. Larger tasks (linting an entire repo, running a full accessibility audit) belong in a real local toolchain, not in a web utility.
Writing
Writing tools for the parts of a draft where the structure, the random pick, or the consistent-sounding name is what is holding you up: generating place and character names against a theme, building world or character tables from a set of independent attributes, picking from a weighted list when the choice does not deserve a real decision. The category is creative-writing-adjacent rather than a substitute for the writing itself; the tools exist so a stuck author can stop chewing on the wrong problem and get back to the sentence. The common misconception is that a name generator's job is to produce a name; the actual job is to produce twenty plausible names so the author can recognize the right one by elimination, which is why every generator here returns a list rather than a single answer. If you are new to the category, start with the name generators when a setting needs a roster of consistent-sounding place or character names, and bookmark the rest as we add them. The category is intentionally small and is expected to grow with dialogue-tag variation, beat-sheet structure helpers, weighted random pickers, and the smaller writing utilities that come up in long-form work. Send a request through the contact page for any pattern you keep hand-rolling.
Find the right calculator.
Each category above groups tools by the job they do: unit conversion sits with math, mortgage and loan payoff with finance, macros and BMI with health. If you know the task but not the tool name, start from the category; if you know the name, the search bar is faster.
Every tool runs in the browser with nothing to install, and each one explains its formula and assumptions below the calculator, so you can check the working instead of trusting a number.