How much does paper weigh?
An 80 gsm A4 sheet weighs 4.99 g; a 500-sheet ream weighs 2.49 kg.
How much does a sheet of paper weigh?
Paper weight is sold in grams per square metre (gsm). A sheet weighs its area in square metres times the gsm. A4 is 210 × 297 mm = 0.06237 m², so an 80 gsm A4 sheet weighs 4.99 g. In theory A0 is exactly 1 m² and A4 is one sixteenth of it, which would give 5 g, but the trimmed sheet is rounded down to whole millimetres, so the real figure is a hair under.
| Paper weight | A3 | A4 | A5 | A6 | US Letter |
|---|---|---|---|---|---|
| 70 gsm | 8.73 g | 4.37 g | 2.18 g | 1.09 g | 4.22 g |
| 80 gsm | 9.98 g | 4.99 g | 2.49 g | 1.24 g | 4.83 g |
| 90 gsm | 11.23 g | 5.61 g | 2.8 g | 1.4 g | 5.43 g |
| 100 gsm | 12.47 g | 6.24 g | 3.11 g | 1.55 g | 6.03 g |
| 120 gsm | 14.97 g | 7.48 g | 3.73 g | 1.86 g | 7.24 g |
| 150 gsm | 18.71 g | 9.36 g | 4.66 g | 2.33 g | 9.05 g |
| 200 gsm | 24.95 g | 12.47 g | 6.22 g | 3.11 g | 12.06 g |
| 250 gsm | 31.19 g | 15.59 g | 7.77 g | 3.88 g | 15.08 g |
| 300 gsm | 37.42 g | 18.71 g | 9.32 g | 4.66 g | 18.1 g |
A4 reams and postage maths
| A4 paper | 500-sheet ream | 100 sheets | Sheets in 100 g |
|---|---|---|---|
| 80 gsm | 2.49 kg | 499 g | 20 |
| 90 gsm | 2.81 kg | 561 g | 18 |
| 100 gsm | 3.12 kg | 624 g | 16 |
| 120 gsm | 3.74 kg | 748 g | 13 |
The ream weights ignore the wrapper, and the sheets-in-100 g figure rounds down to a whole sheet. Envelopes and covers add their own weight, which varies by product, so weigh a sample before relying on it for postage.
Why this works for every A size
Each A size is half the area of the one above it, so the weight halves with each step. If an A4 sheet at 80 gsm is 4.99 g, then A3 is 9.98 g, A5 is 2.49 g and A6 is 1.25 g. The same trick works with the sizes on the paper sizes page. US paper weight (pounds) uses a different basis, so US “20 lb bond” paper is about 75 gsm; do not mix the two without converting.
Frequently asked questions
How much does an A4 sheet weigh?
An 80 gsm A4 sheet weighs 4.99 g.
How much does a ream of A4 paper weigh?
A 500-sheet ream of 80 gsm A4 weighs 2.49 kg without the wrapper.
How much does an A3 sheet weigh?
An 80 gsm A3 sheet weighs 9.98 g.
How much does a sheet of US Letter weigh?
An 80 gsm Letter sheet weighs 4.83 g.
How many sheets of A4 are in 100 g?
About 20 sheets of 80 gsm A4.