Paper Size Converter: A4, Letter and More
The exact size of A4, Letter and other paper sizes in mm, cm and inches, and in pixels.
Good to know. Fold an A4 sheet in half and you get A5 with exactly the same shape. That is the whole idea of the A sizes.
How it works
In plain words
A0 has an area of one square metre, with sides in the ratio 1 : √2. Each next size is the previous one cut in half across its long side, so the shape never changes: A1 is half of A0, A4 is a sixteenth of it.
The formula
A0 = 841 × 1189 mm (1 m²) An+1 = An folded in half · width : height = 1 : √2 pixels = mm ÷ 25.4 × DPI
Worked example
A4 is 210 × 297 mm, which is 8.27 × 11.69 inches, or 2,480 × 3,508 pixels at 300 DPI.
Sources
- ISO 216, Writing paper and certain classes of printed matter: trimmed sizes, A and B series The A and B paper sizes.
Sources checked September 30, 2026. 3 automated tests check its answers on every change.
About the paper size converter: A4, letter and more
Most of the world uses the ISO 216 A sizes, with A4 as the standard sheet for letters and printing. North America uses US Letter, 8½ × 11 inches, which is slightly wider and shorter than A4. This page gives the exact size of each in millimetres, centimetres and inches, and in pixels for designing at a given resolution.
The A sizes are clever: every sheet has sides in the ratio 1 : √2, so cutting one in half gives two sheets of exactly the same shape. A0 is one square metre; A1 is half of that, A2 a quarter, and A4 a sixteenth. That is why an A4 page can be scaled to A3 or A5 on a photocopier without any empty margins.
B sizes sit between the A sizes, for posters and books, and C sizes are envelopes made to hold A sheets: a C4 envelope holds an unfolded A4 sheet, C5 an A4 folded once, and DL an A4 folded in three.
For print, 300 DPI (dots per inch) is the usual resolution; 150 is enough for posters seen from a distance, and 72 or 96 is the classic screen figure. A4 at 300 DPI is 2480 × 3508 pixels.
Questions people ask
What size is A4 in inches?
8.27 × 11.69 inches (210 × 297 mm).
Is A4 the same as Letter?
No. Letter is 8.5 × 11 in (216 × 279 mm): 6 mm wider and 18 mm shorter than A4.
What size is A4 in pixels?
2480 × 3508 pixels at 300 DPI, or 595 × 842 at 72 DPI.