Paper weights (gsm) explained

What gsm means

gsm stands for grams per square metre (sometimes written g/m²). It's the weight of a single sheet of paper one metre by one metre. Because the area is fixed, a higher gsm means denser, usually thicker paper. It's the standard way paper is described in the UK and Europe.

gsm is about weight, not quality. A well-made 80gsm paper can handle ink better than a cheap 100gsm one, because coating and fibre also matter. Treat gsm as a guide to thickness and opacity, then look at how the paper is described.

A quick weight chart

Which weight for which job?

Printing

80gsm A4 is the standard for home and office. Choose 90–100gsm for anything you want to feel a bit special, and check your printer's maximum paper weight before feeding it card.

Fountain pens and gel pens

Wetter inks show through thin paper. Around 90–120gsm usually reduces show-through, but coating is just as important: smooth, sized paper stops ink spreading. Some thin specialist papers perform very well with ink despite their low weight.

Bullet journals

Look for 100gsm or more if you use markers or brush pens. Always test on the back page first.

Cards and crafts

Homemade cards need at least 250gsm to stand up on a shelf. Craft card packs usually state gsm clearly.

Paper sizes in the UK

The A-series sizes are designed so that each size is half of the one above:

You may also see B5 (around 176 × 250mm), a size between A5 and A4 that's popular for student notebooks. For US Letter paper and pound weights, you'd need a different guide; UK retailers almost always use gsm and A-sizes.

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