π Paper Thickness Calculator
From GSM to stack height in one step.
Paper Thickness
How to Use This Paper Thickness Calculator
Enter the paper\'s GSM and how many sheets you have. You get per-sheet thickness in millimeters plus the total stack height in mm, cm, and inches.
Enter the GSM from the paper packaging: 80 for copy paper, 250 for cardstock.
Enter the sheet count: 500 for a ream, or any number for a print job.
Hit Calculate Thickness. Check whether the stack fits your binder, box, or printer tray.
Remember it is an estimate: coated, textured, and handmade papers vary in density.
The Formula
The 0.00125 factor is the typical bulk of uncoated paper: one GSM corresponds to about 1.25 microns of thickness. Real papers range from 0.0008 for dense coated stock to 0.002 for bulky watercolor paper. For ordinary office and craft paper the estimate lands within 10 to 15 percent, close enough for planning.
Worked Example
A 500-sheet ream of 80 GSM copy paper: sheet thickness = 80 x 0.00125 = 0.1 mm. Stack = 500 x 0.1 = 50 mm, which is 5 cm or about 2 inches, matching the familiar ream height. Now 200 sheets of 250 GSM cardstock for invitations: sheet = 0.3125 mm, stack = 62.5 mm or 6.25 cm. That stack needs a deep box and will not fit a standard envelope; the math warns you before the print shop does.
Choosing Paper by GSM
Everyday printing lives at 75 to 90 GSM. Letterheads and resumes feel better at 100 to 120. Flyers and brochures use 130 to 170, postcards 200 to 250, and business cards 300 to 400. Past 300 GSM most home printers give up, so check the manual feed rating. When in doubt, buy a small pack first: paper feel is subjective, and GSM numbers do not capture texture or stiffness.
Paper Weight Around the World
The US also uses basis weight in pounds, which confuses everyone: 20 lb bond is roughly 75 GSM, 80 lb cover is about 215 GSM, and the numbers mean different things for different paper types. GSM is the cleaner system because it measures the same way regardless of sheet size. If a US product lists pounds, look for the GSM equivalent in parentheses; reputable brands print both. For this calculator, always use GSM for consistent and comparable results.
Practical Stack Planning
Binders hold about 100 sheets of copy paper per inch of ring, so a 1-inch binder takes roughly 100 sheets. Mailing: 5 sheets of 80 GSM is about 0.5 mm plus the envelope, safely under most letter thickness limits. Storage boxes: a standard file box holds about 2,500 sheets of copy paper, roughly 25 cm of stack. Envelopes add 0.2 to 0.4 mm per side. Do the stack math before you print 1,000 event programs and discover they fill a crate.
Worked Example: The Wedding Invitation Suite
Invitation card at 250 GSM (0.31 mm per sheet) plus RSVP card at 200 GSM (0.25 mm): each suite is 0.56 mm thick before the envelope. One hundred suites stack to 56 mm, about 2.2 inches, a solid brick of paper that needs a real box, not a bag. Postage warning: anything over a quarter inch thick leaves letter rates for package prices, so a chunky suite with wax seals and liners can double the mailing budget. The thickness math belongs in the stationery budget, not discovered at the post office.
Printer check first: most home printers handle up to 200 GSM through the manual feed, but 300 GSM cardstock jams the standard tray. Test one sheet before buying 200.
Caliper vs. GSM: The Two Measurements
GSM measures weight per square meter; caliper measures actual thickness. They usually move together but not always: a fluffy cotton paper can be thicker than a dense coated sheet at the same GSM. The US printing trade uses points, where 1 point = 0.001 inch, so 10pt cover stock is 0.010 inches thick, roughly 250 GSM territory.
Use GSM when comparing paper heft across brands, and caliper or points when thickness physically matters: envelope stuffing, printer clearance, spine width for booklets. A 100-page booklet on 100 GSM paper needs a spine of about 10 mm; the same pages on 80 GSM need 8. Printers think in caliper; shoppers think in GSM. Now you speak both.
The Fold Test
Before committing to a paper, fold a sheet. Paper under 170 GSM folds cleanly by hand; above that, it cracks along the fold unless scored first. Scoring, a crease pressed with a bone folder or scoring board, gives heavy paper a clean hinge. Wedding suites and greeting cards live or die by the score: an unscored 300 GSM fold looks handmade in the wrong way.
Worked Example: 300-Page Book on 80 GSM
Standard copy paper at 80 GSM measures about 0.10 mm per sheet. A 300-page book is 150 sheets: 150 x 0.10 = 15 mm of paper, plus covers. That is why a typical paperback novel runs about 20 mm thick including the cover boards. Switch to 100 GSM and each sheet is about 0.12 mm; the same 300 pages become 18 mm of paper. The calculator converts GSM to thickness using the paper's bulk, then multiplies by sheet count.
Card stock shows the scale: 300 GSM card is roughly 0.35 to 0.40 mm per sheet, so 100 sheets stack to 35 to 40 mm, a chunky block. This is why business cards feel substantial at 350 GSM and flimsy at 200. When a printer quotes "16pt cover," that is 0.016 inches or about 0.41 mm, in the same territory as heavy card.
Choosing Paper by GSM
GSM is weight per square meter, and it predicts feel better than thickness does. Everyday printing: 75 to 90 GSM. Letterheads and resumes: 100 to 120 GSM, which feeds through printers reliably while feeling deliberate. Brochures: 150 to 170 GSM. Postcards and covers: 250 to 350 GSM. Above 400 GSM you are in board territory that most home printers cannot handle. Match the GSM to the job's handling: anything mailed, folded, or handed out wants the heavier end.
Bulk is the hidden variable: two papers at the same GSM can differ in thickness by 20 percent because one is pressed denser. Uncoated paper is bulkier than coated at the same weight, which is why novels use bulky uncoated stock: more thickness per gram, lower postage per page. If spine width matters for a print run, ask the printer for the specific paper's PPI (pages per inch) rather than converting from GSM yourself.
Frequently Asked Questions
How thick is 80gsm paper?
About 0.1 mm per sheet. Standard copy paper at 75 to 80 GSM measures roughly a tenth of a millimeter, so 100 sheets stack about 10 mm tall. Enter your GSM above for the exact estimate.
How do I convert GSM to mm?
Multiply GSM by about 0.00125 for uncoated paper. So 80 GSM is roughly 0.1 mm and 250 GSM cardstock about 0.31 mm. Coated and specialty papers vary, so treat it as an estimate.
How thick is a ream of paper?
A 500-sheet ream of standard 80 GSM copy paper is about 5 cm, or 2 inches, tall. Heavier paper stacks taller: 500 sheets of 160 GSM is roughly 10 cm. The calculator gives any sheet count.
What does GSM mean for paper?
Grams per square meter: the weight of one square meter of the paper. Higher GSM means thicker, stiffer paper. Copy paper is 75 to 90 GSM, cardstock 200 to 300, and business cards 300 to 400.
How thick is cardstock in mm?
About 0.25 to 0.35 mm for typical 200 to 300 GSM cardstock. Heavy 400 GSM board reaches about 0.5 mm. Craft projects that layer cardstock add up fast, so check the stack math above.
Is higher GSM always thicker?
Usually but not always. Density varies: a dense 200 GSM coated sheet can be thinner than a fluffy 180 GSM watercolor paper. GSM measures weight, thickness measures caliper, and bulk is the ratio between them.
How many sheets are in an inch of paper?
About 250 sheets of standard 80 GSM copy paper per inch, since each sheet is roughly 0.1 mm. Cardstock at 0.3 mm fits about 85 sheets per inch. The calculator converts any count to height.
What paper thickness do printers handle?
Most home printers handle 60 to 160 GSM through the main tray. Heavier cardstock up to 250-plus GSM usually needs the manual feed or rear tray. Check your printer's specs before forcing thick stock through.