Paper Weight From GSM Calculator
Calculate the weight of one paper sheet from its GSM and size. Choose A4, A3, Letter, Legal, or enter custom dimensions to get grams per sheet.
Last updated: July 2026
Weight of one sheet
Calculated sheet weight
Calculation
Sheet weight = width (m) × height (m) × GSM
This is the theoretical weight from the entered nominal GSM and dimensions. Manufactured sheets can vary slightly.
Common paper-size areas
| Size | Dimensions | Area |
|---|---|---|
| A3 | 297 × 420 mm | 0.12474 m² |
| A4 | 210 × 297 mm | 0.06237 m² |
| A5 | 148 × 210 mm | 0.03108 m² |
| US Letter | 8.5 × 11 in | 0.060322 m² |
| US Legal | 8.5 × 14 in | 0.076774 m² |
| US Tabloid / Ledger | 11 × 17 in | 0.120645 m² |
How to calculate paper weight from GSM
The weight of one rectangular sheet is its area in square meters multiplied by its grammage:
Sheet weight (g) = width (m) × height (m) × GSM
For millimeter dimensions, use width (mm) × height (mm) × GSM ÷ 1,000,000. For an A4 sheet at 80 GSM: 210 × 297 × 80 ÷ 1,000,000 = 4.9896 g.
What does GSM mean in paper?
GSM stands for grams per square meter (g/m²). It does not mean that one sheet weighs that many grams. An 80 GSM material has a nominal mass of 80 grams for each square meter; an A4 sheet covers 0.06237 m², so it weighs about 4.99 g.
Same GSM, different sheet weight
Two sheets can have the same GSM and different weights because their areas differ. A3 has approximately twice the area of A4, so A3 at a given GSM weighs approximately twice as much as A4 at that GSM. Orientation does not affect area or weight.
GSM also does not directly specify thickness. Material, coatings, density, and construction can produce different thicknesses at the same grammage.
Worked examples
A4 at 80 GSM
A4 is 210 × 297 mm, or 0.210 × 0.297 m. Its area is 0.06237 m². Therefore, 0.06237 × 80 = 4.9896 g, displayed as 4.99 g or approximately 0.176 oz per sheet.
A3 at 120 GSM
A3 is 297 × 420 mm. Its area is 0.12474 m², so 0.12474 × 120 = 14.9688 g, displayed as 14.97 g or approximately 0.528 oz.
US Letter at 75 GSM
Using the exact conversion of 0.0254 meter per inch, 8.5 × 11 inches becomes 0.2159 × 0.2794 m. The area is 0.06032246 m², so one sheet weighs 4.5241845 g, displayed as 4.52 g or approximately 0.160 oz.
Custom 100 × 150 mm at 300 GSM
The area is 0.100 × 0.150 = 0.015 m². Multiplying by 300 g/m² gives 4.5 g for one sheet.
What this calculator does—and does not—calculate
This calculator finds the theoretical weight of one sheet from nominal GSM and physical dimensions. It does not calculate quantities, stacks, reams, cartons, packaging, shipping weight, thickness, cost, or US basis weight. Actual manufactured sheets may vary slightly from nominal specifications.
Frequently asked questions
How do I calculate the weight of one sheet from GSM?
Convert width and height to meters, multiply them to find square meters, then multiply that area by GSM.
How much does one A4 sheet of 80 GSM paper weigh?
Approximately 4.99 grams.
Does 80 GSM mean one sheet weighs 80 grams?
No. It means one square meter of the paper has a nominal mass of 80 grams. A smaller finished sheet weighs proportionally less.
Does paper size affect weight if GSM stays the same?
Yes. A larger sheet has more area and therefore weighs more at the same GSM.
Can I calculate custom paper sizes?
Yes. Choose custom size, enter positive width and height values, and select millimeters, centimeters, or inches.
Is GSM the same as paper thickness?
No. GSM measures mass per unit area. Thickness also depends on material, density, coatings, and construction.