What Is GSM Paper? Meaning and Weight Chart

GSM at a Glance: 80 to 300 GSM

The six weights below are the ones that come up most often in a print brief. Each line gives the typical use; the full chart in the next section covers the wider ranges, including folding carton board.

Related: Brochure vs catalogue · Catalogue print specs · Brochure Printing

1. GSM Chart: Common Paper Weights and Uses

These are the conventional ranges used across commercial printing. They are starting points for a conversation, not rules — a heavier stock is not automatically a better one, and specifying 400 GSM where 300 GSM would do adds cost and freight without adding perceived quality. Note that folding cartons and rigid boxes sit in a different category from paper: cartons are cut from paperboard specified in GSM, while rigid boxes use a greyboard core specified in millimetres.

Related: Business Cards · Mono Cartons · Rigid Gift Boxes

2. What GSM Actually Measures

GSM is a measure of mass per unit area, and that is all it is. It says nothing directly about how thick a sheet feels, how stiff it is, or how opaque it is. This matters because buyers routinely use GSM as shorthand for thickness, and then get a result that does not match what they pictured. A 300 GSM coated art card and a 300 GSM uncoated textured card weigh the same, but the uncoated sheet will usually be visibly and tangibly thicker, because the mineral coating on the art card adds weight without adding much height. If the physical thickness of the sheet is what matters to your design, the number to ask for is calliper, quoted in microns, not GSM.

3. GSM, Calliper and Bulk: Three Different Numbers

Three properties get conflated in print briefs, and separating them removes most of the confusion. GSM is weight. Calliper is thickness, measured in microns, and is what determines whether a business card feels substantial between finger and thumb. Bulk is the relationship between the two — a high-bulk paper achieves more thickness for the same weight, which is why some paperback novels feel chunky despite using light stock. When you are specifying a job, decide which of the three actually matters. For a mailed brochure where postage is a real cost, GSM is the number to control. For a business card where the tactile impression is the entire point, calliper is what you should be asking about.

Related: Get a quote for your print job

GSM to lb: Converting to US Paper Weights

US paper suppliers quote weight in pounds, based on the weight of a ream of a basis sheet size, and the basis size is different for text and cover stock. That is why the same paper has two lb figures. The conversions below are the standard factors; round to the nearest stock the mill actually makes. There is no fixed conversion from GSM to inches or millimetres of thickness, because thickness depends on the paper's bulk: ask for the calliper, or use the calculator in this guide to estimate it.

4. Coated, Uncoated and Textured: Why the Same GSM Feels Different

Coating changes almost everything about how a given GSM behaves. A coated art paper has a mineral layer applied to the surface, which holds ink on top of the sheet rather than letting it sink in. That produces sharper images and stronger colour, and it is why photography-led catalogues are almost always printed on coated stock. Uncoated papers absorb ink into the fibre, which softens the image slightly and shifts colours a little duller, but they take a pen and feel warmer to the touch. Textured and laid papers add a further variable: the surface relief scatters light and can break up fine detail, so small type and hairline rules need care. When comparing quotes, make sure you are comparing the same surface as well as the same weight.

• Coated gloss: highest ink holdout and colour saturation, most reflective, can be tiring to read at length.
• Coated matte and silk: same colour strength as gloss with far less glare, the usual choice for text-heavy premium work.
• Uncoated: writable, warmer, softer image, needs a heavier weight to achieve the same perceived substance.
• Textured and laid: distinctive hand-feel, but avoid for fine serif type and dense photographic detail.

5. Folding, Creasing and the Cracking Threshold

Creasing is a mechanical operation that compresses the fibres along a line so the sheet folds cleanly instead of tearing. On lighter stock the fibres can absorb a fold without help. Past roughly 170 GSM they cannot, and the result is the ragged white line along a spine that makes an expensive brochure look cheap. The problem is worse on coated stock, because the coating layer has no give at all, and worse again on dark covers, where any exposed white fibre is obvious. If a job has a heavy coated cover in a dark colour, laminating before folding is the usual insurance: the film holds the surface fibres together across the fold. This is one of the most common causes of avoidable disappointment in brochure printing, and it is entirely preventable at the specification stage.

6. Opacity and Show-Through on Double-Sided Work

Opacity is measured as a percentage and describes how much light passes through a sheet. It is a separate property from GSM, though the two correlate loosely. For double-sided printing, opacity is the number that decides whether the reverse side ghosts through and makes the page harder to read. Heavy solid blocks of colour show through far more than text, so a design with full-bleed dark panels on both sides of the same leaf needs more opacity than a text-only document at the same weight. If a catalogue design puts photography on both sides of every page, discuss opacity explicitly rather than simply raising the GSM, because a bulkier sheet at the same opacity will not solve it.

7. How GSM Interacts with Cost and Freight

Paper is typically the largest single material input in a print job, and it is bought by weight. Moving a 5,000-copy catalogue from 130 GSM to 170 GSM inners raises the paper weight of the job by roughly a third, and that increase flows through both the material cost and the freight cost of delivering the finished cartons. This is worth modelling before the specification is frozen, particularly for anything being shipped across the country or mailed individually. The practical advice is to put the weight where it will be felt: a heavier cover with lighter inners usually delivers more perceived quality per rupee than raising every page uniformly.