What does GSM mean on paper?

GSM is grams per square metre — the mass of a one-metre-by-one-metre sheet of that paper, regardless of how it is cut. It is the international way to describe paper weight because it does not depend on sheet size. Standard office copy paper is 80 gsm, a flyer is around 130 gsm, and a business card is about 300 gsm. Higher GSM usually means thicker and stiffer, though coating and fibre can change the feel at the same weight.

How do I convert GSM to pounds (lb)?

You need the paper grade, because US basis weight is the weight of a 500-sheet ream cut to that grade's basis size. The formula is lb = gsm × (width × height in inches) ÷ 1406.5. For Text/Book stock (25 × 38 in) that makes 120 gsm ≈ 81 lb. Pick the grade in the tool, type the GSM, and it does the arithmetic — no chart lookup, no guessing which basis size applies.

Why do different paper grades use different conversion factors?

Each US grade is weighed on its own basis size: Bond/Writing on 17 × 22 in, Text/Book on 25 × 38 in, Cover on 20 × 26 in, Index on 25.5 × 30.5 in. The pound number is the weight of 500 sheets at that size, so the same physical paper carries a different lb label per grade. That is why 20 lb Bond (about 75 gsm) and 20 lb Cover (about 54 gsm) are not the same thickness — the GSM number cuts through that confusion.

What does an 80 gsm sheet of A4 paper weigh?

About 4.99 grams. An A4 sheet is 21 × 29.7 cm, which is 0.06237 square metres, and 80 gsm means 80 grams per square metre, so 80 × 0.06237 ≈ 4.99 g. That is why a 500-sheet ream of 80 gsm A4 weighs roughly 2.5 kg. Use the single-sheet panel to get the weight for any size and GSM — handy for postage, where one extra gram can push a letter into the next price band.

What is the difference between Cover and Text weight paper?

Text (or Book) weight is the lighter stock used for letterheads, brochures and book pages, typically 60 to 100 lb text (about 90 to 150 gsm). Cover weight is the heavy stock for business cards, postcards and folders, often 60 to 120 lb cover (about 160 to 325 gsm). Because they use different basis sizes, you cannot compare the pound numbers directly — convert both to GSM first and the heavier card is obvious.

Is higher GSM always thicker paper?

Usually, but not always. GSM measures weight per area, not thickness. Two papers at 250 gsm can differ in caliper because one is bulkier (more air, looser fibre) and the other is dense and calendered. Coated glossy stock often feels thinner than uncoated stock of the same GSM. For most everyday choices GSM is a fine proxy for sturdiness; for precise thickness, printers also quote caliper in microns or points.

Order print stock from a US shop while thinking in GSM

You design in Europe in GSM but the print shop quotes everything in pounds. You want a 300 gsm business card and a 150 gsm brochure. Pick Cover for the card and Text for the brochure, type the GSM, and read the pound labels the shop expects — about 110 lb cover and 100 lb text. Now your spec speaks their language and nothing gets pressed on the wrong stock.

Check postage before a mailing goes out

A mailing of A4 letters has to stay under a weight band or the postage jumps. Type your GSM and pick A4 in the sheet panel — 80 gsm reads about 4.99 g per sheet, 100 gsm about 6.24 g. Multiply by the page count plus the envelope and you know which postage tier you land in before you print a thousand copies and find out at the counter.

Compare two paper quotes given in different units

One supplier quotes 24 lb Bond, another quotes 90 gsm. Are they the same paper? Convert the 24 lb Bond to GSM (about 90 gsm) and you can see they are effectively identical, so you can decide on price alone instead of guessing whether one is heavier than the other.

Spec a self-published book interior and cover

You are laying out a paperback. The interior wants a readable but not bulky text stock and the cover needs to feel substantial. Convert your target GSM for each — say 90 gsm interior, 250 gsm cover — into the lb values your print-on-demand service lists, and lock the spec before uploading so the proof matches what you imagined.

Paper Weight GSM Calculator — GSM to lb Converter

GSM ⇄ US basis weight (lb) by paper grade, plus single-sheet weight from sheet size — browser-only

Runs locally
Category Format Converter
Best for Turning pasted content or local files into a handoff-friendly format.

Convert paper weight between metric GSM (g/m²) and US basis weight (lb). Pick the paper grade first — a pound of Bond and a pound of Cover are cut to different basis sizes, so they map to very different GSM. Type GSM or pounds and the other updates live. The sheet-weight panel below tells you what a single cut sheet actually weighs.

Paper grade

Basis size: 25 × 38 in

GSM (g/m²)

↔

Basis weight (lb)

120 g/m² = 81.07 lb · Text / Book

Single-sheet weight

How much one cut sheet weighs at the GSM above. Pick a size or type your own (cm).

Common sizes:

Sheet size W (cm)

H (cm)

One sheet weighs

7.484g

Common paper weights

Common paper weights	GSM	lb (Text / Book)
Lightweight / airmail	60	40.5
Standard copy / printer	80	54
Premium letterhead	100	67.6
Flyer / brochure	130	87.8
Thin card / postcard	200	135.1
Business card / cover	300	202.7

25 × 38 in

What this tool does

Free paper weight calculator that converts between metric GSM (grams per square metre) and US basis weight in pounds, the right way: by paper grade. A pound of Bond and a pound of Cover are weighed on different basis sizes, so "20 lb" means two completely different thicknesses depending on the grade. Pick Bond, Text, Cover, Index, Tag or Bristol, type a GSM or a pound value, and the matching number updates live. The conversion uses gsm = lb × 1406.5 ÷ (width × height of the grade basis size in inches), so 120 gsm text stock reads as about 81 lb and a 20 lb bond writing paper reads as about 75 gsm. A second panel computes what a single cut sheet actually weighs — pick A4, A3, Letter or A5, or type your own size in centimetres, and it returns the weight in grams (an 80 gsm A4 sheet is about 4.99 g). A reference table maps common weights from 60 gsm airmail to 300 gsm card. Everything runs in your browser, one-click copy and a shareable URL that reopens the same grade and value. 100% client-side, no upload.

Tool details

Input: Numbers; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 9 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Format Converter · Designer; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How Paper Weight GSM Calculator fits into your work

Use it when the main problem is getting content from one practical format into another.

Conversion jobs

Turning pasted content or local files into a handoff-friendly format.
Previewing a conversion before you use it in a larger workflow.
Cleaning small format mismatches without opening a full editor.

Conversion checks

Try a small sample first when the source format is messy.
Check character encoding, separators, and line endings after conversion.
Keep the source until the converted output has been reviewed.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Order print stock from a US shop while thinking in GSM
You design in Europe in GSM but the print shop quotes everything in pounds. You want a 300 gsm business card and a 150 gsm brochure. Pick Cover for the card and Text for the brochure, type the GSM, and read the pound labels the shop expects — about 110 lb cover and 100 lb text. Now your spec speaks their language and nothing gets pressed on the wrong stock.
Check postage before a mailing goes out
A mailing of A4 letters has to stay under a weight band or the postage jumps. Type your GSM and pick A4 in the sheet panel — 80 gsm reads about 4.99 g per sheet, 100 gsm about 6.24 g. Multiply by the page count plus the envelope and you know which postage tier you land in before you print a thousand copies and find out at the counter.
Compare two paper quotes given in different units
One supplier quotes 24 lb Bond, another quotes 90 gsm. Are they the same paper? Convert the 24 lb Bond to GSM (about 90 gsm) and you can see they are effectively identical, so you can decide on price alone instead of guessing whether one is heavier than the other.
Spec a self-published book interior and cover
You are laying out a paperback. The interior wants a readable but not bulky text stock and the cover needs to feel substantial. Convert your target GSM for each — say 90 gsm interior, 250 gsm cover — into the lb values your print-on-demand service lists, and lock the spec before uploading so the proof matches what you imagined.

Common pitfalls

Converting GSM to pounds without picking a grade. There is no single gsm-to-lb factor — 200 gsm is about 135 lb index but only 74 lb cover. Always choose Bond, Text, Cover or Index first, or the pound number is meaningless.
Comparing pound numbers across grades directly. 80 lb text and 80 lb cover are nowhere near the same thickness because they use different basis sizes. Convert both to GSM before deciding which paper is heavier.
Mixing up sheet weight units. The single-sheet panel takes centimetres and returns grams. Feeding it inches or millimetres without converting gives a weight that is off by orders of magnitude, which throws off postage math.

Privacy

Every calculation — the gsm-to-pound formula, the per-grade basis factors and the single-sheet weight — is plain JavaScript that runs in your browser tab. No paper spec, size or value ever leaves the page, and there is no logging of what you converted. The one caveat: the shareable URL encodes your GSM value and chosen grade in the query string, so a link pasted into chat will record those in the recipient server's access log. That is harmless for paper weights, but worth knowing the URL carries your inputs.

FAQ

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Paper Weight GSM Calculator — GSM to lb Converter

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How Paper Weight GSM Calculator fits into your work

Conversion jobs

Conversion checks

Good next steps

Real-world use cases

Order print stock from a US shop while thinking in GSM

Check postage before a mailing goes out

Compare two paper quotes given in different units

Spec a self-published book interior and cover

Common pitfalls

Privacy

FAQ

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