Convert paper weight between GSM, lb, points, and mm — instantly, across every packaging category at once.
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Some mills use a different basis size than the one implied above, and rigid/gift-box board has no basis size at all. Fill this in to enable an exact Lbs (per ream) figure for the primary result.
Enter a value in any field and get instant conversions.
grams / m² — direct & exact
for the category selected — exact
caliper — estimate only
from points — estimate only
Corrugated "test" (200#) and ECT ratings are not paper weight — they rate a box's burst/stacking strength, not the linerboard's basis weight. Full explanation in the guide below the tool.
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GSM (grams per square meter) is paper's direct weight-per-area measurement — the same number means the same thickness everywhere. US "basis weight" (lb) instead measures the weight of 500 sheets (a ream) cut to that paper category's own standard size, so the same lb number is a different thickness in different categories.
To convert: GSM = (lb × 1406.5) ÷ basis sheet area. Or skip the math and use the converter above — it now handles GSM, lb, points, and mm together, live.
GSM (grams per square meter) is a direct, universal measure of paper's mass per unit area — a 100 gsm sheet weighs 100 grams for every square meter of it, regardless of paper type. It's the standard measurement almost everywhere outside North America.
In the US, paper is traditionally sold by "basis weight" in pounds instead — but a basis weight in lb only makes sense once you know the basis sheet size it refers to, because it's defined as the weight of 500 sheets (a ream) cut to that category's standard size. That's why "24 lb" bond paper and "24 lb" cover stock are actually very different thicknesses: bond paper's basis size is 17×22 in, while cover stock's is 20×26 in — a bigger basis sheet means each individual sheet in the "24 lb" cover ream is thinner than a sheet in the "24 lb" bond ream, even though the ream weighs the same.
| Category | Basis sheet size | Typically used for |
|---|---|---|
| Bond / Writing | 17 × 22 in | Letterhead, forms, writing paper |
| Text / Book | 25 × 38 in | Brochures, catalogs, book text pages |
| Cover | 20 × 26 in | Postcards, folders, folding carton stock, business cards |
| Index / Bristol | 25½ × 30½ in | Index cards, light tags, light board |
| Tag / Kraft | 24 × 36 in | Kraft paper, hang tags, void-fill sheets |
Note: some mills use a separate "Bristol" basis size (22½ × 28½ in) distinct from "Index Bristol." If a supplier's spec sheet doesn't match the numbers above, use the converter's "advanced: override basis size" option, or ask them which basis size they're quoting against before ordering.
The exact relationship, used throughout the North American paper industry:
GSM = (lb weight × 1406.5) ÷ basis sheet area (sq in)
lb weight = (GSM × basis sheet area) ÷ 1406.5
This is why the converter above asks you to pick a category first — the same GSM value produces a different lb number in every category, because each one is divided by a different basis area.
Flat kraft paper (used for void-fill, wrapping, and light bags) is sold in the US the same way as tag stock — by basis weight in lb, on a 24 × 36 in basis sheet — commonly seen as 30#, 40#, 50#, 60#, 70#, or 80# kraft. In grams per square meter, that's roughly:
Corrugated board is different again. The linerboard and fluting medium that make up corrugated board are rated by basis weight in pounds per 1,000 square feet (MSF) — standard linerboard weights are 26, 33, 38, 42, 47, 56, 69, and 90 lb; medium (fluting) typically runs 23–40 lb. This is a separate measurement basis from the sheet-lb system above, and isn't directly interchangeable with it.
These numbers describe how a finished box performs, not how heavy its paper is. Mullen burst test ratings (200#, 275#, 350#) measure how much pressure the board can take before rupturing — useful for rough handling and puncture resistance. ECT (Edge Crush Test) ratings (32 ECT, 44 ECT) measure stacking/compression strength, which matters more for palletized shipping. A "200# test" box is typically built from around 42 lb basis-weight linerboard — but the "200" and the "42" are not the same kind of number, and treating a test/ECT rating as if it were a basis weight (or a GSM figure) is one of the most common mix-ups in corrugated specs. If a supplier gives you a test or ECT rating, that's a box construction spec, not a paper weight you can look up on this chart.
| Material | Typical range | Notes |
|---|---|---|
| Tissue paper | 10–40 gsm | Gift wrap, void-fill, interleaving |
| Kraft paper — light | 30–40 lb (≈49–65 gsm) | Light wrap, small bags |
| Kraft paper — medium | 50–60 lb (≈81–98 gsm) | General-purpose wrap and void-fill |
| Kraft paper — heavy | 70–80 lb (≈114–130 gsm) | Heavier bags, higher-durability wrap |
| Cardstock / cover stock | ≈250–360 gsm (12–18pt) | Folding cartons, hang tags, inserts |
| Chipboard / rigid box board | ≈600–2,500+ gsm | Rigid gift boxes, usually specified by thickness (mm) or points rather than lb |
| Corrugated linerboard | 26–90 lb per MSF | Different basis (per 1,000 sq ft) — not directly comparable to the rows above |
| Corrugated medium (fluting) | 23–40 lb per MSF | Same MSF basis as linerboard |
"Points" (or caliper) measure physical thickness, not weight: 1 point = 0.001 inch = 0.0254 mm — an exact physical conversion, not an estimate. An "18pt" cardstock is 0.018 inch (0.457 mm) thick. This is a different kind of measurement from GSM or lb — GSM measures mass per area, while points and mm measure how thick the sheet is — and the two aren't strictly interchangeable, because a denser board can be thinner but heavier than a fluffier one at the same weight.
That said, for standard folding-carton board, published GSM-to-points references are commonly close to the ones below. Treat these as approximate, manufacturer-dependent reference points rather than an exact formula — always confirm caliper with your actual supplier's spec sheet before finalizing packaging.
| GSM | Points (≈ est.) | Thickness mm (≈ est.) | Typical use |
|---|---|---|---|
| 216 gsm | ≈8 pt | ≈0.20 mm | Light cover stock, folders |
| 300 gsm | ≈14 pt | ≈0.35 mm | Standard folding cartons |
| 350 gsm | ≈17 pt | ≈0.43 mm | Premium folding cartons |
| 400 gsm | ≈21 pt | ≈0.53 mm | Heavy cover, light rigid inserts |
| 454 gsm | ≈24 pt | ≈0.61 mm | Thick cardstock, display board |
These rows use the same approximate GSM↔points model as the "≈ est." fields in the converter above — good for planning, but always confirm exact caliper against your supplier's actual spec sheet before finalizing a print run.
Not sure which weight is right for your product?
Get a free quote →The basis sheet sizes, the GSM/lb conversion constant, and the corrugated linerboard and medium weight ranges above follow standard US paper-trade basis-weight conventions and standard corrugated-industry weight tables — the same references our own sourcing team checks supplier spec sheets against day to day. The GSM-to-points/mm figures are a separate, approximate reference for standard folding-carton board furnish, clearly marked as an estimate throughout this page and the converter, since exact caliper varies by manufacturer and paper stock.
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