A paper sizes chart: A0 to A10 in mm, inches and pixels

Exact dimensions for every ISO A size, the pixel sizes you need at common DPI settings, and why halving a sheet always gives you the next size down.

Updated 9 October 2026 · 6 min read

A0 to A10 in millimetres, centimetres and inches

The millimetre values are the official ones from ISO 216. The inch values are converted (1 inch = 25.4 mm) and rounded to two decimals, so they are not "round" numbers. Sizes are always written width × height in portrait orientation.

A0 to A10 in pixels at 72, 150 and 300 DPI

A paper size has no pixel size of its own. Pixels only appear once you decide how many dots you want per inch. The formula is pixels = millimetres ÷ 25.4 × DPI, rounded to the nearest whole pixel. These are the values for the three most common settings:

• 300 DPI is the usual target for anything printed and looked at up close: documents, flyers, photos, booklets.
• 150 DPI is often enough for posters and large prints viewed from a step or two away, and for draft prints.
• 72 DPI is the old "screen" default. It is what many PDF tools use when they talk about page size in points (1 point = 1/72 inch), which is why an A4 PDF page is reported as 595 × 842.

For any other DPI, or to see a size in centimetres or inches at a click, use the paper size converter. If you are starting from a picture and want to know how big it will print, the DPI calculator does the reverse sum.

How the A series works

The system is built on two rules, which is why the numbers look slightly odd but fit together perfectly:

1. A0 has an area of one square metre. 841 × 1189 mm = 0.99995 m², as close to one as whole millimetres allow.
2. Every sheet has the same proportions, 1 : √2 (about 1 : 1.414). That is the only ratio that stays the same when you cut a sheet in half across its long side.

So each size is made by halving the previous one: the long side of A(n+1) is the short side of A(n), and the short side is half the long side of A(n), rounded down to the millimetre. A4 is 210 × 297; halve 297 and you get 148.5, rounded down to 148, so A5 is 148 × 210.

Because the proportions never change, you can enlarge or reduce between A sizes without cropping or leaving margins. That is what the preset scaling buttons on photocopiers do:

One step changes the length of each side by √2 (×1.414 or ×0.707) and the area by exactly two. Two steps double or halve each side.

What each A size is used for

A sizes vs US Letter and other sizes

The USA, Canada and a few other countries use inch-based sizes instead. The closest equivalents are:

• A4 vs Letter: Letter is 8.5 × 11 in (215.9 × 279.4 mm). It is about 6 mm wider and 18 mm shorter than A4. Documents made for one usually print on the other with a little scaling or a bigger bottom margin.
• A3 vs Tabloid (Ledger): Tabloid is 11 × 17 in (279.4 × 431.8 mm), slightly narrower and longer than A3.
• A5 vs Half Letter: Half Letter (Statement) is 5.5 × 8.5 in (139.7 × 215.9 mm).

There are also B sizes, which sit between the A sizes (B4 is between A3 and A4), and C sizes for envelopes: a C4 envelope takes a flat A4 sheet, C5 takes A4 folded once, C6 takes A4 folded twice. The converter lists all of them.

Common mistakes when designing for A sizes

• Forgetting bleed. If colour runs to the edge of the page, print shops usually ask for 2–5 mm of extra image on every side (3 mm is the most common request). An A4 page with 3 mm bleed is 216 × 303 mm, or 2551 × 3579 px at 300 DPI. Check the printer's own spec.
• Designing at 72 DPI and printing at A4. A 595 × 842 px image fills an A4 page only at 72 DPI and will look soft on paper. Start at 2480 × 3508 px if the result is for print.
• Mixing up portrait and landscape. A4 landscape is 297 × 210 mm, or 3508 × 2480 px at 300 DPI. Same numbers, swapped.
• Home printer margins. Most desktop printers cannot print right to the edge, so keep important content a few millimetres in from every side.

Frequently asked questions