320+ sizes · 23 series · every unit

Every paper size, measured and explained.

Dimensions in millimetres, inches and pixels for every paper, envelope, photo and card size in use, drawn to scale, with tools that do the printer maths for you.

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ISO A series

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Inches
Pixels @300 dpi
Area
Ratio

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Every size is exactly half of the one before it. Hover a sheet to see the fold that makes the next one.

Fold any ISO sheet in half and you get the next size down, with exactly the same proportions. That single rule is why A4 is the shape it is.

Start with the standard you use

Every series has a chart with all its sizes, a to-scale diagram and a printable PDF. Not sure which you use? Standard printer paper is Letter in the US and Canada and A4 almost everywhere else.

All series →

ISO A seriesThe ISO A series runs from A0 (841 × 1189 mm, one square metre) down to A10 (26…13 sizes · ISO 216 North American sizesNorth American paper is built around Letter (8.5 × 11 in, 215.9 × 279.4 mm), Legal (8.5 ×…11 sizes · ANSI/ASME Y14.1 and trade EnvelopesEnvelope sizes follow the paper they carry. ISO envelopes (C series and DL) are built around A4 and…39 sizes Photo print sizesPhoto prints use inch-based R sizes: 4R is 4 × 6 in (101.6 × 152.4 mm), 5R is…24 sizes · Trade standard ISO B seriesThe ISO B series fills the gaps between A sizes. B0 is 1000 × 1414 mm, and each…11 sizes · ISO 216 Card sizesCard sizes span bank cards, business cards, postcards, index cards and playing cards. ISO 7810 ID-1 is 85.6…17 sizes · ISO 7810 and trade Book sizesBook sizes are trade names, not ISO sizes. UK paperbacks use A format (110 × 178 mm), B…17 sizes · Trade standard Regional & historical sizesRegional and historical sizes are the national systems that predate ISO 216 or fill local gaps: Japanese JIS…124 sizes

Tools

Stop guessing at the printer dialog

All tools →

Paper Size FinderMeasure any sheet, type the two numbers, and find out exactly which paper size it is, plus the closest standards if it is a near miss.Open tool Paper Size ConverterAny paper size in millimetres, centimetres, inches, points, picas and pixels at the DPI you choose. Custom dimensions welcome.Open tool Paper Scale CalculatorThe exact percentage to enlarge or reduce a page from one size to another, with a warning when you need to rotate first.Open tool Pixel & DPI CalculatorPixels needed for any print size at any resolution, or the largest print your image can make without going soft.Open tool

How it works

Three rules explain almost every size on this site

A0 is one square metre. Every ISO size is a fraction of it, which is why paper weight in grams per square metre works so neatly.
The sides are in the ratio 1 : √2. Halve the long side and the proportions do not change. Scaling A4 to A3 is always 141%.
North America kept the inch. Letter is 8½ × 11 in, not a fraction of anything, so it never scales cleanly. That is the whole A4 vs Letter problem.

Read the full guide to ISO 216 →