Paper Weight Converter
Convert paper weight between grams per square metre and the US basis-weight scales used for text, bond, cover, index, bristol and tag. Enter a value, choose the units, then press Convert.
About the Paper Weight Converter
GSM is the honest measurement: the mass of one square metre of paper. US basis weight is the mass of a ream of 500 sheets in a particular untrimmed size, and that size changes with the paper grade. A 100 lb cover is not the same paper as a 100 lb text — the cover sheet is smaller, so each pound represents more weight per area.
That is why the same 216 gsm sheet can be called 80 lb text, 80 lb bond or 60 lb cover depending on which trade is describing it. This converter uses the standard basis sizes: 17 × 22 in for bond, writing and text; 20 × 26 in for cover; 25.5 × 30.5 in for index; 22.5 × 28.5 in for bristol; and 24 × 36 in for tag.
How the calculation works
- GSM = basis weight × 1,406.2 ÷ (basis sheet area in square inches).
- 1 lb text or bond = 3.759 gsm; 1 lb cover = 2.704 gsm.
- 1 lb index = 1.808 gsm; 1 lb bristol = 2.192 gsm.
- 1 lb tag = 1.628 gsm.
Reference values
| Paper grade | Basis sheet | 1 lb equals | Common name |
|---|---|---|---|
| Text / book | 17 × 22 in | 3.759 gsm | 80 lb text ≈ 104 gsm |
| Bond / writing | 17 × 22 in | 3.759 gsm | 20 lb bond ≈ 75 gsm |
| Cover | 20 × 26 in | 2.704 gsm | 80 lb cover ≈ 216 gsm |
| Index | 25.5 × 30.5 in | 1.808 gsm | 110 lb index ≈ 199 gsm |
| Bristol | 22.5 × 28.5 in | 2.192 gsm | 67 lb bristol ≈ 147 gsm |
| Tag | 24 × 36 in | 1.628 gsm | 100 lb tag ≈ 163 gsm |
Worked example: text, cover and card
80 lb text is 80 × 3.759 = 301 gsm, not 80 gsm. 80 lb cover is 80 × 2.704 = 216 gsm. A 100 lb cover is 270 gsm, while a 100 lb text is 376 gsm—so the grade matters as much as the number. For a business card, 300–350 gsm is a common weight.
When a printer asks for a “100 lb card”, confirm whether they mean cover or index. The same number describes different thicknesses in different grades, and the finished feel depends on bulk and finish as well as mass. If the specification is critical, ask for the gsm figure.