90 lb index paper
163 g/m²
90 lb index · basis size 25.5 × 30.5 in · Index cards, tabbed dividers and stiff record cards.
Where 163 gsm comes from
An American basis weight is the weight of 500 sheets at that grade's basis size. For index that size is 25.5 × 30.5 inches, so:
500 sheets × 25.5 × 30.5 in = 388,875 in² = 250.9 m²
90 lb = 40,823 g
40,823 g ÷ 250.9 m² = 163 g/m²The same number, a different paper
90 lb is not one weight. Because every grade is weighed at its own sheet size, the same pound figure describes papers that are nothing alike:
| Grade | Basis size | 90 lb is | vs index |
|---|---|---|---|
| Index | 25.5 × 30.5 in | 163 gsm | — |
| Bond / Writing | 17 × 22 in | 338 gsm | 2.08× |
| Text / Book | 25 × 38 in | 133 gsm | 0.82× |
| Cover | 20 × 26 in | 243 gsm | 1.50× |
| Tag | 24 × 36 in | 146 gsm | 0.90× |
| Bristol | 22.5 × 28.5 in | 197 gsm | 1.21× |
This is the reason to ask for gsm. One number, no grade, no ambiguity — 163 gsm is 163 gsm whoever is printing it.
Frequently asked questions
What is 90 lb index paper in gsm?
163 gsm. 90 lb means 500 sheets at the index basis size of 25.5 × 30.5 inches weigh 90 pounds.
Is 90 lb index the same as 90 lb bond?
No, and the difference is large. 90 lb index is 163 gsm; 90 lb bond is 338 gsm — 2.08 times as heavy. The pound number is the weight of 500 sheets at a size that differs by grade, so it cannot be compared across them.
What is 90 lb index used for?
Index cards, tabbed dividers and stiff record cards. At 163 gsm: board rather than paper, needing a press with a straight paper path.