Paper Size Reference
ISO A- and B-series, envelope sizes (C4, C5, DL…) and common US paper sizes, in millimetres and inches.
Last updated
ISO A-series
| Size | Millimetres | Inches |
|---|
ISO B-series
| Size | Millimetres | Inches |
|---|
Envelopes
| Size | Millimetres | Inches |
|---|
US sizes
| Size | Millimetres | Inches |
|---|
How to use the paper size chart
- Find the size you need in the A, B, envelope or US tables.
- Read its width and height in millimetres and inches.
About this tool
The ISO 216 A-series is built on one rule: each size is exactly half of the one before it, cut along the long edge, and every size shares the same aspect ratio (1:√2 ≈ 1:1.414) — which is why an A4 sheet folded in half becomes an A5 sheet with identical proportions. US paper sizes (Letter, Legal, Tabloid) don't follow this rule and use a different, non-constant aspect ratio, which is why scaling a US Letter document to A4 (or vice versa) always crops or adds a small margin rather than matching exactly.
B sizes sit between the A sizes (B5 is between A4 and A5) and are used for posters, books and passports. C-series envelopes are made to fit the matching A sheet: a C4 envelope takes an A4 sheet flat, a C5 takes A4 folded once, and a DL takes A4 folded into thirds — the usual business letter.
This is a static reference — nothing here involves a server, and it runs entirely in your browser tab.
Questions about paper sizes
What size is A4 paper?
210 × 297 mm, or 8.27 × 11.69 inches. It’s the standard letter and printer paper size almost everywhere except North America.
What is the difference between A4 and US Letter?
Letter is 8.5 × 11 inches (216 × 279 mm): a little wider and shorter than A4. Documents scaled from one to the other gain or lose a small margin.
How big is A3 or A5?
A3 is 297 × 420 mm, twice the size of A4. A5 is 148 × 210 mm, half of A4. Each A size is half the one before.
Which envelope fits A4?
C4 takes A4 flat, C5 takes A4 folded once, and DL takes A4 folded into thirds, the usual business letter.