Paper Calculator

A paper calculator converts between the two systems used to state paper weight and derives the properties that follow from it: caliper (thickness), weight per sheet and per ream, and cost per page. US basis weight is the weight in pounds of 500 sheets cut to the grade's basis size, while grammage (gsm) is the weight in grams of one square meter of the sheet, so the same pound figure describes a different paper in each grade. All numeric inputs accept decimals, fractions such as 3/4, and mixed numbers such as 1 1/2.

Each grade has its own basis size: bond and writing 17 x 22 in, book and text 25 x 38 in, cover 20 x 26 in, bristol 22.5 x 28.5 in, index 25.5 x 30.5 in, and tag, newsprint, tissue, and kraft 24 x 36 in. That is why 80 lb text (118.4 gsm) is far lighter than 80 lb cover (216.3 gsm). The conversion is gsm = pounds x 453.592 / (500 x basis area in square meters), which works out to about 1,406.1 divided by the basis area in square inches, so 20 lb bond is 20 x 1,406.1 / 374 = 75.2 gsm. Sheet sizes include Letter, Legal, Tabloid, A4, A3, and custom dimensions in inches, millimeters, or centimeters.

Caliper is estimated from basis weight with a points-per-pound factor for each grade, fitted to published mill calipers for uncoated stock: 0.19 for bond (20 lb is about 3.8 pt), 0.075 for text, 0.14 for cover, 0.13 for bristol, 0.078 for index, 0.07 for tag, and 0.105 for newsprint, with tissue and kraft as rougher estimates. One point is 0.001 inch, or 0.0254 mm. Coated papers are denser, so a gloss, satin, or matte sheet measures thinner than the estimate at the same weight; coated book runs about 3 to 5.5 pt from 60 to 120 lb. The estimated caliper falls into one of eight thickness options, each with its typical applications, from tissue and interleaving under 2 pt to packaging board above 14 pt. The limit checker compares grammage and estimated caliper against a minimum, a maximum, or both, such as a printer's supported media range or the 7 to 16 pt thickness that postcard rates require.

Sheet weight scales the basis weight by area: weight per sheet = pounds x (sheet area / basis area) / 500. A ream is 500 sheets, so a ream of letter-size 20 lb bond weighs 20 x (93.5 / 374) = 5 lb. Cost per page is the ream price divided by 500, and the total cost is the cost per page times the number of sheets. The finish adds a description of the surface, its ink behavior, and its usual jobs, and Settings holds the decimal places and a step-by-step view of each conversion.

80 lb cover on Letter converts to 80 x 1,406.1 / 520 = 216.3 gsm. The estimated caliper is 80 x 0.14 = 11.2 pt (0.28 mm), which falls in the 10 to 14 pt range for business cards and heavy postcards and passes a 7 to 16 pt postcard check. One sheet weighs 80 x (93.5 / 520) / 500 = 0.02877 lb, or 13.05 g, so a ream weighs 14.38 lb. At $30 per ream, each sheet costs $0.06.

Paper selection decisions involve thickness, weight, cost, and surface finish. Matching these properties to the intended print run or project prevents waste, ensures the correct look and feel, and controls budget.

• Print Production: Comparing 60 lb and 80 lb book text shows the grammage and caliper the heavier sheet adds (88.8 against 118.4 gsm), which a print buyer weighs against the opacity a double-sided magazine layout needs to avoid show-through.
• Office Procurement: 20 lb bond at 10 reams (5,000 sheets) with a ream price forecasts quarterly paper spend for a department. Moving to 24 lb bond shows the cost and thickness increase for client-facing letterhead.
• Packaging Design: Finding the cover weights that land near 10 and 12 pt narrows the stock options for a folding carton prototype before samples are ordered for rigidity testing and a full print run.
• Direct Mail: Postcard-rate mail must be 0.007 to 0.016 inch thick under USPS rules. With 7 and 16 pt as the thickness limits, 65 lb cover at an estimated 9.1 pt qualifies, while 100 lb text at about 7.5 pt sits close to the floor and is worth confirming against the mill caliper.
• Publishing: A 300-page book printed on 50 lb text has 150 leaves. At a 6 x 9 in trim each leaf weighs 50 x (54 / 950) / 500 = 0.00568 lb, so the text block weighs about 0.85 lb before the cover, which feeds shipping carton counts and freight cost per unit.
• Invitation and Stationery: Compare uncoated vellum finish on 80 lb cover stock against linen finish on 100 lb cover to decide which combination delivers the desired tactile impression for wedding invitations.
• Printer Compatibility: Office printers and copiers list a supported media range in gsm. Setting that range as the weight limits shows at once whether a heavy cover stock will feed, before a ream is bought.
• Education: Demonstrate the relationship between basis weight, basis size, and gsm conversion to students learning print production or graphic communications coursework.
• Sustainability Auditing: Dropping a print run from 24 lb to 20 lb bond cuts paper weight by a sixth for the same sheet count, which supports material reduction reporting with a total weight saved per run.