GSM vs lb: paper weight explained
Paper weight should be simple, but the US pound system makes it a trap: 80 lb Text and 80 lb Cover are wildly different papers. GSM — grams per square metre — is the unambiguous measure the rest of the world uses. Here's how both work and how to compare stocks without getting burned.
GSM: one honest number
GSM (g/m²) is literally the weight of one square metre of the paper, regardless of grade or sheet size. Higher GSM generally means thicker, stiffer, heavier stock. Copy paper is around 80 gsm; a sturdy flyer is 130–170 gsm; a business card is 300–400 gsm.
Because it's grade-independent, GSM lets you compare any two papers directly. This is exactly why most of the world specifies paper in GSM and why it's the safest number to put on a print order.
Why US pounds are confusing
A US 'basis weight' is the weight of 500 sheets (a ream) of that grade cut to its basic size — and the basic size is different for every grade. Bond's basic size is 17 × 22 in; Cover's is 20 × 26 in; Text's is 25 × 38 in. Same 500 sheets, different sheet dimensions, so the pound numbers aren't comparable across grades.
| Spec | Approx GSM | Typical use |
|---|---|---|
| 20 lb Bond | ≈ 75 gsm | Copy / office paper |
| 80 lb Text | ≈ 118 gsm | Brochure / book interior |
| 80 lb Cover | ≈ 216 gsm | Postcards / covers |
| 100 lb Cover | ≈ 270 gsm | Heavy cards |
| 110 lb Index | ≈ 200 gsm | Tabs / dividers |
Weight is not the same as thickness
Two papers at the same GSM can have different calipers (thickness) because of bulk — how the fibres are packed. Uncoated and 'rough' stocks bulk up thicker than dense coated papers of the same weight. That matters when thickness drives a result, like a book spine.
If you're estimating a spine, weight alone won't do it; you need the paper's caliper. Our spine width calculator uses page count and stock so you don't have to guess.
Coated vs uncoated
A 150 gsm gloss text and a 150 gsm uncoated text weigh the same but feel different — the uncoated sheet is usually thicker and more opaque. Always feel a printed sample before committing a long run.
Comparing stocks across vendors
When two printers quote different pound numbers, convert both to GSM and compare like-for-like. A converter that knows each grade's basic size removes the arithmetic and the errors — the paper weight converter handles Bond, Text, Cover, Index, Tag and Bristol and shows the full equivalents table.
Frequently asked questions
Is GSM or lb more accurate?
GSM is unambiguous because it's a direct measure of weight per area. Pound weights are accurate within a single grade but can't be compared across grades without knowing each grade's basic size.
What GSM is a good business card?
Most business cards are 300–400 gsm so they feel rigid. 350 gsm is a common sweet spot. Below ~250 gsm a card feels flimsy.
Why is 80 lb Cover so much heavier than 80 lb Text?
Because each grade's pound weight is measured on a different basic sheet size. Cover's basic size is much smaller than Text's, so reaching the same ream weight requires far heavier paper — about 216 gsm vs 118 gsm.
Does higher GSM always mean thicker?
Usually, but not always. Bulk and coating affect thickness, so a heavily calendered coated sheet can be thinner than an uncoated sheet of equal GSM. For thickness-critical jobs, check caliper, not just weight.
Why we quote in GSM
Pound weights have caused more mix-ups in our quotes than any other number, which is why we put GSM on everything. One honest figure beats six grade-specific ones. Reviewed June 14, 2026.