Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Convert paper weight from GSM to pounds for any basis size.
21.27 lbs
Equivalent Weight (always shown)
GSM (grams per square meter) is the international standard for describing paper weight -- a single, unambiguous number regardless of sheet size. The US "pounds" system is different and genuinely confusing: it's the weight of a ream (500 sheets) at that paper category's specific standard "basis size," which varies by paper type. That means "20 lb" bond paper and "20 lb" cover paper are not the same actual thickness -- this converter handles that correctly by asking which basis size applies.
Enter your paper's GSM value and select its basis size category: Bond (17×22in, the default), Text (25×38in), Cover (20×26in), Index (25.5×30.5in), Bristol (22.5×28.5in), or Tag (24×36in). The result shows pounds for your selected basis size, plus equivalent weights in Bond, Cover, and Index pounds simultaneously -- so you can compare a spec sheet regardless of which basis size it uses.
Factor = 1406.5 ÷ (Basis Length (in) × Basis Width (in))
Pounds = GSM ÷ Factor
1406.5 is a standard constant relating grams-per-square-meter to pounds-per-ream for a given basis sheet size (it accounts for the area of 500 sheets at that basis size, converted from metric to US units). Because each paper category's basis sheet has different dimensions, the same GSM converts to a different pounds figure depending on which category you're in -- which is exactly why this converter asks for a basis size instead of using one fixed multiplier.
| Category | Basis Size | Typical Use |
|---|---|---|
| Bond | 17 × 22in | Letterhead, copy paper, writing paper |
| Text | 25 × 38in | Brochures, magazine interiors |
| Cover | 20 × 26in | Business cards, postcards, book covers |
| Index | 25.5 × 30.5in | Index cards, tabs, file folders |
| Bristol | 22.5 × 28.5in | Cardstock, presentation materials |
| Tag | 24 × 36in | Tags, heavy-duty labels |
Print shops and designers comparing a European supplier's GSM spec against a US paper stock's pound rating. Anyone ordering business cards, letterhead, or brochures who needs to match a specific paper thickness across different suppliers' labeling systems.
Always confirm which basis size a "lb" rating refers to before comparing paper weights -- "80 lb cover" and "80 lb text" are very different actual thicknesses, since they're measured against different basis sheet sizes. This is one of the most common sources of confusion when ordering print materials.
The same GSM figure produces different pound ratings depending on the paper category, so it helps to see a few side by side. These are hypothetical stock choices used only to illustrate the formula.
Notice that 120 GSM reads as roughly 32 lb on the Bond basis but about 81 lb on the Text basis. Neither is wrong; they describe the same sheet weight against different reference sheets.
Pick the category that the printer or paper merchant uses for that stock. Copy paper, letterhead, and notepads are almost always sold on the Bond basis. Brochure interiors and magazine pages are usually Text. Business cards, postcards, and folders are typically Cover. If you are unsure, check the paper's product name: a listing that says something like 80 lb Cover or 100 lb Text is telling you the basis in the name. When only a bare weight appears, ask the supplier.
The extra Bond, Cover, and Index figures shown alongside your result are the fastest way to compare stocks. If a US catalog lists a card stock at 65 lb Cover and your European printer offers 175 GSM, converting 175 GSM gives about 64.7 lb Cover, so the two are effectively the same weight. Close is close enough; suppliers round their specifications, and manufacturing tolerances mean the actual weight can differ slightly from the label.
GSM and pounds measure mass per area, not caliper (thickness). Two papers of identical GSM can feel different because of coating, fiber content, and finishing. Uncoated stock tends to be bulkier per gram than a heavily coated gloss stock. If thickness matters, for example for a book spine or an envelope insertion, ask the supplier for the caliper rather than inferring it from GSM alone.
The calculation is a straight area-based conversion using the constant 1406.5, so it reflects the definition of each basis size, not a measurement of any specific sheet. Real-world paper can vary by a few percent from its nominal weight, and some mills round their pound ratings to convenient values. For an important print run, ask your printer for a sample and confirm the specification in writing.
Because the "lb" rating is the weight of 500 sheets at that paper category's own standard basis size (Bond, Text, Cover, etc.) -- since those basis sizes differ, the same nominal "lb" number corresponds to a different actual thickness across categories.
GSM (grams per square meter) is the international, size-independent standard for paper weight, widely used outside the US and increasingly in professional printing specs everywhere since it avoids the basis-size ambiguity of the pound system.
Use the Bond, Cover, and Index equivalent figures this converter shows alongside your selected basis size's result -- they let you compare "lb" ratings across categories on a common footing.
On the Bond basis it is about 26.58 lb. On other bases the figure differs, which is why the calculator asks for a category.
It is a common heavier card weight, equivalent to about 110.9 lb Cover. Whether it suits your design depends on your printer's stocks and the feel you want.
Because the Cover basis sheet is larger in area than the Bond sheet, the same paper gets a different pound number. The physical paper is unchanged.
Usually heavier paper is stiffer, but coating, fiber, and finish also affect stiffness and thickness, so GSM is only a guide.
Reference: NIST Weights and Measures