Paper Weight Calculator
Weigh a stack of paper without a scale. Enter the sheet count, pick a size (US Letter, Legal, Tabloid, or A4) and a stock (20-32 lb bond, 65 lb cover, or 110 lb index), and get the total in pounds or ounces and grams, the per-sheet weight, and how many sheets mail on one First-Class ounce.
Example: with Number of sheets 500 · Sheet size US Letter (8.5 × 11 in) · Paper stock 20 lb bond / 75 gsm — standard copy paper → Total weight: 5.00 lb (2.27 kg).
- Per sheet4.54 g (0.160 oz)
- Postage check6 sheets stay under 1 oz bare; inside a #10 envelope (≈ 6.75 g), figure 4 sheets per First-Class ounce
Computed by the calculator below using its default values. Change any input to see your own numbers.
Weight = gsm × sheet area × count. A ream of standard copy paper weighs 5.00 lb — exactly a quarter of its "20 lb" rating, because Letter is a quarter of the 17 × 22 in basis sheet.
Why "20 lb paper" does not weigh 20 pounds
US paper weights rate 500 sheets of the grade's basis size, not the size in your printer. Bond paper's basis sheet is 17 × 22 inches — exactly four Letter sheets — so a ream of 20 lb copy paper weighs 20 ÷ 4 = 5.00 lb. Cover stock uses a 20 × 26 in basis and index uses 25.5 × 30.5, which is why a "65 lb cover" is dramatically heavier stock than "32 lb bond" despite the numbers suggesting otherwise.
Grams per square meter (gsm) cuts through all of it: one number, one square meter, any grade. This calculator converts each stock to gsm (20 lb bond = 75.2 gsm) and multiplies by the actual sheet area, so Letter, Legal, Tabloid, and A4 all compute honestly.
How it’s calculated
Weight = gsm × sheet area (m²) × sheet count. Areas: Letter 0.06032 m², Legal 0.07677, Tabloid 0.12064, A4 0.06237. Bond gsm comes from the basis weight — 500 sheets of 17 × 22 in weigh the rated pounds — giving 20 lb = 75.2 gsm, 24 lb = 90.2, 28 lb = 105.3, 32 lb = 120.3; cover (65 lb = 176 gsm) and index (110 lb = 199 gsm) use their own basis sizes per published conversions. 1 lb = 453.59237 g; 1 oz = 28.3495 g; a #10 envelope weighs about 6.75 g.
Ignores ink and humidity — toner adds a fraction of a gram per page, and paper stored humid can run a few percent heavy.
What a ream (500 Letter sheets) weighs
| Stock | gsm | Per sheet | Ream |
|---|---|---|---|
| 20 lb bond | 75.2 | 4.54 g | 5.00 lb |
| 24 lb bond | 90.2 | 5.44 g | 6.00 lb |
| 28 lb bond | 105.3 | 6.35 g | 7.00 lb |
| 32 lb bond | 120.3 | 7.26 g | 8.00 lb |
| 65 lb cover | 176 | 10.62 g | 11.70 lb |
| 110 lb index | 199 | 12.00 g | 13.23 lb |
Computed as gsm × 0.06032 m² × 500. Bond reams land at exactly a quarter of the rated weight because Letter is a quarter of the 17 × 22 in basis sheet.
Common mistakes
- Expecting a "20 lb" ream to weigh 20 lb — the rating covers 500 sheets of the 17 × 22 in basis size; the Letter ream weighs 5 lb.
- Comparing pounds across grades: 65 lb cover is far heavier stock than 32 lb bond because each grade rates a different basis sheet.
- Forgetting the envelope in postage math — a #10 envelope spends about 6.75 g of your 28.35 g First-Class ounce.
- Mixing gsm and lb in one comparison; convert everything to gsm first.
Frequently asked questions
What is the paper weight formula?
Weight = gsm × sheet area in square meters × number of sheets. One Letter sheet of 20 lb bond: 75.2 gsm × 0.0603 m² = 4.54 g, so a 500-sheet ream is 2,268 g — 5.00 lb.
How much does a ream of paper weigh?
A ream (500 sheets) of standard 20 lb Letter copy paper weighs 5.00 lb (2.27 kg). Heavier stocks scale up: 24 lb bond is 6 lb per ream, 32 lb is 8 lb.
How many sheets can I mail with one stamp?
A First-Class letter rate covers 1 oz (28.35 g). A #10 envelope uses about 6.75 g, leaving room for 4 sheets of 20 lb paper; the fifth sheet tips you into the additional-ounce rate.
What is the difference between lb and gsm?
gsm is absolute — grams per square meter of that exact paper. US pounds rate 500 sheets of each grade's basis size, which differs by grade, so 65 lb cover (176 gsm) outweighs 32 lb bond (120 gsm) sheet for sheet.