Paper sizes, A4, letter and the rest in mm, inches and pixels.

A4 paper is 210 mm wide and 297 mm tall, which is 8.27 × 11.69 inches. US letter paper is 8.5 × 11 inches, which is 215.9 × 279.4 mm. Almost every country outside North America uses the ISO A series, and the US and Canada use letter, legal and ledger. Use the picker above for any size on this page, in portrait or landscape.

How to use the converter

1. Choose a size in Size. The big card shows millimetres, centimetres, inches and pixels.
2. Switch Direction between portrait and landscape, or press Turn sideways.
3. Set Resolution (dpi), or press one of the dpi buttons, to see the pixel size to design or scan at.
4. Type a width and a height under Find a size to see the three closest named sizes. Click one to load it.
5. Copy size and Copy link keep the answer. Click any row of the table to load that size.

How the A series works

Every A size has the same shape: the long side divided by the short side is the square root of two, about 1.414. A0 has an area of one square metre. Cut any A sheet in half across its long side and you get the next size down, with the same shape. So an A4 sheet is two A5 sheets, four A6 sheets and eight A7 sheets. Sizes are whole millimetres, found by halving and rounding down: A0 is 841 × 1189 mm, so A1 is 594 × 841 (1189 ÷ 2 = 594.5, rounded down to 594). Check: 841 × 1189 = 999,949 mm², very close to 1 m².

A series in full

B and C series

B sizes sit between A sizes: B1 is the geometric mean of A0 and A1. They are used for posters, books and some envelopes. C sizes sit between A and B of the same number and are used for envelopes, so a C4 envelope takes an A4 sheet flat. B0 is 1000 × 1414 mm and C0 is 917 × 1297 mm.

US and JIS sizes

The Japanese JIS B4 is 257 × 364 mm and JIS B5 is 182 × 257 mm. They are a little bigger than ISO B4 (250 × 353) and B5 (176 × 250).

A4 against letter

Letter is 5.9 mm wider than A4 and 17.6 mm shorter. So a document made for one size does not fit the other without a margin change: A4 is longer and narrower, letter is shorter and wider. Their areas are close: A4 is 62,370 mm² and letter is 60322 mm², so A4 has about 3.4 percent more. If you print an A4 file on letter paper, choose "fit to page" or the bottom lines will be cut.

Pixels for a paper size

Pixels are inches times dpi. A4 at 300 dpi is 2480 × 3508 px, since 210 ÷ 25.4 × 300 = 2,480.3 and 297 ÷ 25.4 × 300 = 3,507.9. At 150 dpi it is 1240 × 1754 px, and at 72 dpi it is 595 × 842 px. Letter at 300 dpi is 2,550 × 3,300 px. A higher dpi means a bigger file, so 300 is a common choice for print and 150 for drafts. Convert units with the inches to cm converter.

Worked examples

• How many A5 pages fit on A4? Two, side by side, because A4 cut in half is A5. Four A6 pages fit as well.
• A poster at A2. 420 × 594 mm, which is 16.54 × 23.39 in. At 150 dpi that is 2,480 × 3,508 px.
• A 5 × 7 inch card. 127 × 177.8 mm, bigger than A6 (105 × 148) and smaller than A5 (148 × 210).
• A C5 envelope. 162 × 229 mm, which takes an A5 sheet flat or an A4 sheet folded once.

Where the numbers come from

The ISO sizes follow the ISO 216 rule as set out by Markus Kuhn, University of Cambridge: International standard paper sizes: A0 has an area of one square metre, the sides are in the ratio of the square root of two, and each size is the long side halved and rounded down to whole millimetres. B and C sizes start from 1000 × 1414 mm and 917 × 1297 mm. The W3C W3C CSS Paged Media Module Level 3 states A5, A4, A3, B5, B4 (ISO), JIS B5 (182 × 257) and JIS B4 (257 × 364), and letter (8.5 × 11 in), legal (8.5 × 14 in) and ledger (11 × 17 in). Both pages were read on 24 Oct 2026. The ISO page for the standard itself would not load, and the standard text is paid, so it was not read. Sizes not named here, such as other US sheet sizes, are not stated and not included.

Related pages: PPI calculator, Inches to cm, Cm to inches and Image resizer.