GSM to Thickness Calculator

Weight is not thickness.

Weight is not thickness. GSM measures weight per square metre, not thickness.

Written and maintained by Mohit PatelLast checked August 4, 2026How we build these

Paper weight

gsm

Bulk factor

Sheet width

Sheet height

Sheets

Approximate thickness

330 µm

0.330 mm per sheet

Weight per sheet18.71 g

Thickness per sheet0.330 mm

Stack height165.0 mm

Total weight9.36 kg

GSM measures weight per square metre, not thickness, two papers at the same weight can differ substantially in thickness depending on bulk. The bulk factor varies from about 0.8 for coated stock to 1.5 or more for uncoated and textured papers, so treat this as an estimate.

How the GSM to Thickness Calculator works

GSM measures weight per square metre, not thickness. Two papers at the same weight can differ substantially in thickness depending on bulk, coated stocks are dense and thin, uncoated and textured ones are the opposite.

Also known as: paper weight to thickness · GSM paper calculator · card thickness from GSM

Weight is not thickness

GSM is grams per square metre, a measure of weight. Thickness is measured in microns or in points. They correlate and they are not the same thing, and paper is bought on the first while it feels like the second.

The bridge between them is bulk, expressed in cubic centimetres per gram, which describes how much volume a gram of that paper occupies. Thickness equals GSM times bulk.

Two papers at the same GSM can differ noticeably in thickness because their bulk differs. Uncoated papers generally have higher bulk than coated ones, so a 150 gsm uncoated sheet feels thicker than a 150 gsm gloss sheet.

Typical weights and what they are used for

Around 80 to 100 gsm is office paper and letterheads. 120 to 170 is flyers and posters. 250 to 350 is business cards, postcards and covers. Above 350 is heavy card, folders and premium cards.

Books use lower weights for the text block, typically 70 to 100 gsm, because the page count multiplies the weight and the postage.

Packaging is measured differently, usually in board grades and flute types for corrugated, where the structural performance matters more than the weight.

Coated against uncoated

Coated paper has a mineral layer that seals the surface, holding ink on top rather than letting it absorb. That gives sharper detail, more saturated colour and a smoother feel.

Uncoated absorbs, which spreads ink slightly and softens fine detail. Colours print less vividly and the surface takes writing, which coated stock does not without a special finish.

Neither is better. Coated suits photography and colour work; uncoated suits text, anything to be written on, and designs where a tactile natural feel is part of the intent. Choosing on habit rather than on the piece is how a beautifully photographed brochure ends up looking flat.

Opacity and show-through

Thin paper printed both sides shows the reverse through, which is distracting and looks cheap. Opacity is a measured property and it does not track weight exactly, since some papers are formulated to be opaque at low weight.

The practical threshold for double-sided printing is around 100 gsm for text and higher where there are large solid areas of ink.

Where a low weight is required for postage or page count, an opaque grade is worth specifying explicitly. It costs more per sheet and prevents the outcome where a saving on paper produces a document nobody wants to read.

The postage threshold

Paper weight determines postage, and postal services price in bands with sharp edges. A mailing that crosses a threshold costs meaningfully more per item.

Working backwards from the postage band is worth doing before specifying the stock. Total weight is the sheets plus the envelope plus any insert, and it is easy to exceed a band by a few grams.

The same applies to thickness, since several postal services price large letters by thickness as well as weight. A mailing designed at 5 millimetres when the threshold is 5 millimetres will fail on some items and pass on others, which produces a surcharge on part of the run and a query on the rest.

Where to go next

The GSM to Thickness question rarely arrives on its own. These are the ones that usually come with it:

Print File Size Calculator — Doubling DPI quadruples the file.
Bleed and Margin Calculator — Document size, trim size and safe area.
Packaging Cost Calculator — Better packaging can pay for itself in damage.
Etsy Fee Calculator — Every Etsy fee on one sale, itemised.

Not financial advice. Marketplace fees change, and they vary by country, plan and seller status. Every rate here is an editable default, not a quoted price, check the platform's current fee schedule before you price a product against it. This is not tax or business advice.

Frequently asked questions

What does GSM mean?

Grams per square metre, the weight of one square metre of the paper. It is a weight measure that people use as a proxy for thickness.

How do I convert GSM to thickness?

Multiply by the bulk factor, which varies from around 0.8 for coated stock to 1.5 or more for uncoated and textured. Without knowing the bulk, the conversion is an estimate.