Paper Size Converter
Paper sizes vary significantly between the US and the rest of the world. The ISO 216 standard (used in over 150 countries) defines A-series paper where each size is half the area of the previous. The US uses ANSI standard sizes (Letter, Legal, Tabloid) with different aspect ratios. This converter shows the dimensions of any selected paper size in both millimeters and inches, and lets you compare sizes side by side.
Paper size standards
ISO A0: 841 mm x 1189 mm | Each An = An-1 halved on long axis | Aspect ratio = 1:sqrt(2)
US Letter = 8.5 in x 11 in = 215.9 mm x 279.4 mm. 1 inch = 25.4 mm exactly (NIST). All ISO A-series dimensions are rounded to the nearest millimeter per ISO 216.
Common paper size dimensions
- A0: 841 x 1,189 mm (33.1 x 46.8 in). Engineering drawings, posters.
- A1: 594 x 841 mm (23.4 x 33.1 in). Architectural drawings, flip charts.
- A3: 297 x 420 mm (11.7 x 16.5 in). Tabloid-equivalent, newspapers.
- A4: 210 x 297 mm (8.27 x 11.69 in). Standard document size worldwide.
- US Letter: 215.9 x 279.4 mm (8.5 x 11 in). Standard US document size.
- US Legal: 215.9 x 355.6 mm (8.5 x 14 in). US legal and government forms.
Paper size converter: frequently asked questions
What is the difference between A4 and US Letter?
A4 (ISO 216) is 210 mm x 297 mm (8.27 in x 11.69 in). US Letter is 8.5 in x 11 in (215.9 mm x 279.4 mm). Letter is wider and shorter than A4. Most of the world uses A4; the US and Canada primarily use Letter. Documents formatted for one may have margins cut off when printed on the other.
How is the ISO A-series defined?
ISO 216 defines A0 as having area exactly 1 m2 and aspect ratio sqrt(2):1 (approximately 1.4142). Each subsequent size (A1, A2, ...) is obtained by folding the previous size in half along its longer dimension. A0 is 841 mm x 1189 mm; A4 is 210 mm x 297 mm.
What is Tabloid paper used for?
Tabloid paper (11 in x 17 in, also called Ledger when used in landscape) is used for newspapers, large spreadsheets, engineering drawings, and posters in the US. It is approximately equivalent to A3 (297 mm x 420 mm) but slightly smaller.
What is Legal paper?
US Legal paper is 8.5 in x 14 in (215.9 mm x 355.6 mm). It is longer than Letter (8.5 x 11) and is used for legal documents, contracts, and some government forms. It has no direct ISO equivalent but is closest to F4 (215 mm x 330 mm) used in some Asian countries.
What is the ratio between A-series paper sizes?
The dimensions of A(n) are exactly half those of A(n-1) in one dimension. The long side of A1 = short side of A0, and the short side of A1 = half the long side of A0. All A-series sheets share the same aspect ratio of 1:sqrt(2).
Official sources
- ISO 216:2007: Referenced via NIST SP 811: Guide for the Use of the International System of Units (SI).
- NIST inch definition: NIST Handbook 44.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.