Drywall Calculator

Drywall quantity comes down to one number: the net square footage of board to hang, divided by the coverage of a single panel. This calculator builds that number from as many rooms or surfaces as a job contains, subtracts the openings listed for each, adds a waste allowance, and rounds up to whole panels. Every area entry is independent, so a basement with three differently sized rooms and a stairwell wall can be estimated in one pass.

• Measurement units. Feet is the default. Switching units converts every already-entered value rather than reinterpreting it, so 12 entered as feet becomes 3.6576 after switching to meters.
• Area method. Length x Width x Height treats an entry as a room, with wall area at 2 x (Length + Width) x Height; including the ceiling adds Length x Width on top of the walls. Leaving Height blank turns the entry into a flat rectangle of Length x Width, which is how a single wall, a ceiling, or a soffit face gets entered. Square footage takes an area already known from a plan or a takeoff, read in the squared version of the selected unit.
• Doors and windows. A count and the size of one opening are multiplied and subtracted from the gross area. Defaults are a 3 by 6.75 foot door and a 3 by 4 foot window. Leaving the counts at zero hangs board across the full wall, which is what many installers do when the cutout becomes scrap anyway.
• Multiple areas. Each room or surface is its own entry, optionally named (Master Bedroom, Stairwell), and duplicated rather than retyped when several rooms share the same dimensions, so a basement with several rooms and a stairwell wall totals in one pass.
• Panel size. Thirteen standard sizes run from 4 by 8 feet through 4 by 16 feet, including 54 inch wide sheets sold for 9 foot walls, plus a custom width and length. Panel dimensions are always read in feet, since board is sold in imperial sizes regardless of the measurement unit used for the rooms.
• Waste allowance. Ten percent is a common starting point for a straightforward room. It runs higher for rooms with many openings, angles, or short runs, or down to zero to see the bare requirement.
• Cost per panel. Prices the rounded panel count, not the fractional one, since whole sheets are what get bought.

Wall area equals 2 times (Length plus Width) times Height. Ceiling area equals Length times Width. Openings equal (door count times door width times door height) plus (window count times window width times window height). Net area equals gross area minus openings. Panels to buy equals the ceiling of net area times (1 plus waste percent divided by 100), divided by panel area. All numeric fields accept decimals (0.75), fractions (3/4), mixed numbers (5 1/16 or 1-3/8), and scientific notation (1.5e3); currency symbols, commas, and percent signs are stripped before parsing.

A 12 by 10 foot room at 8 feet high, with the ceiling included, has a wall area of 2 times (12 plus 10) times 8, or 352 square feet, plus a 120 square foot ceiling (12 times 10), for 472 square feet gross. One door (3 by 6.75 feet) and one window (3 by 4 feet) subtract 20.25 and 12 square feet, for 32.25 square feet of openings, leaving 439.75 square feet net. A 10 percent waste allowance brings that to 483.725 square feet, and at 32 square feet per 4 by 8 foot panel, 483.725 divided by 32 is 15.12, which rounds up to 16 panels.

Drywall is bought in whole sheets and delivered in a single drop, so the cost of guessing runs in both directions: a short order stops the job for a supply run, and a long order leaves sheets warping against a garage wall. The scenarios below cover the takeoffs this calculator is shaped for, from a single patch wall to a whole floor of a house.

• Single room remodel: A 12 by 10 foot room at 8 feet high, ceiling included, with one door and one window deducted, nets 439.75 square feet. At 4 by 8 foot panels with 10 percent waste, that returns 16 panels.
• Whole floor takeoff: A whole floor sums one entry per room, with repeated bedroom sizes duplicated rather than re-entered; the per-area breakdown reports gross, openings, net, and panel count for each room separately, showing which room drives the order.
• Garage or shop with tall walls: 4 by 12 or 4 by 16 foot panels hang a 10 or 12 foot wall in a single vertical sheet; comparing the panel count against 4 by 8 foot sheets shows how many butt joints the longer sheet removes.
• Ceiling only: Room length and width entered with height left blank reduces the entry to a flat rectangle, the ceiling area on its own.
• Fire rated or moisture rated assemblies: The board area comes first, with required thickness and layer count confirmed against local code separately. A two-layer assembly needs the panel count doubled by hand, since layering is not built into the panel total.
• Contractor quoting: A cost per panel from a current supplier sheet, priced in the matching currency, gives a material subtotal that updates directly with the waste allowance, useful for showing a client the difference between a 5 percent and a 15 percent allowance.
• Metric plans: Room dimensions taken straight off a metric drawing work in meters, while panel sizes stay imperial because that is how board is sold in North America; net area reports in square feet, square meters, and three other units.
• Finishing material budget: Screw count, screw weight, joint compound buckets, and tape length all derive from the net board area, with every underlying rate exposed and editable rather than fixed.
• Repair and patch work: A measured patch area entered directly as square footage, with waste set to zero, shows whether the repair takes one sheet or two.