Paper Size Converter
Compare international paper sizes.
Input
Result
What is a Paper Size Converter?
A Paper Size Converter is a free online tool that compares and converts paper sizes across different international standards, including the ISO A series (A0 to A10), US Letter, Legal, Tabloid, and other common formats. It shows dimensions in millimetres, inches, and pixels at various resolutions.
How to calculate paper size conversion manually (the formula)
ISO A series sizes follow a simple rule: each size is half the area of the previous size. A0 has an area of 1 m² with dimensions 841 mm × 1189 mm. A1 is 594 mm × 841 mm (half of A0). To find the next size, divide the longer side by 2 to get the shorter side of the next size.
Example calculation
A0: 841 mm × 1189 mm (1 m²). A1: 594 mm × 841 mm (0.5 m²). A2: 420 mm × 594 mm (0.25 m²). A3: 297 mm × 420 mm (0.125 m²). A4: 210 mm × 297 mm (0.0625 m²).
Common mistakes
- Confusing A4 with US Letter — A4 (210 × 297 mm) and US Letter (215.9 × 279.4 mm) are close in size but not interchangeable. A4 is narrower and taller.
- Assuming all A series sizes are proportional by length — While each A size is half the area, the dimensions do not halve uniformly. The aspect ratio remains √2:1.
- Using wrong units — Paper sizes are specified in millimetres in ISO standards. Converting to inches introduces rounding errors.
Frequently asked questions
What is a Paper Size Converter?
A Paper Size Converter is a tool that compares and converts paper sizes across international standards, including ISO A series (A0 to A10), US Letter, Legal, and Tabloid sizes.
What are the standard ISO paper sizes?
The ISO A series includes A0 (841 × 1189 mm), A1 (594 × 841 mm), A2 (420 × 594 mm), A3 (297 × 420 mm), A4 (210 × 297 mm), A5 (148 × 210 mm), and smaller sizes down to A10.
How does A4 compare to US Letter size?
A4 is 210 × 297 mm, while US Letter is 215.9 × 279.4 mm. A4 is slightly narrower and taller than US Letter.
What size is A0 in millimetres?
A0 paper measures 841 × 1189 millimetres, with an area of exactly 1 square metre.
How are ISO paper sizes related?
Each ISO A size is half the area of the previous size. A1 is half of A0, A2 is half of A1, and so on. The aspect ratio is always √2:1.