Paper Size Chart
Every common paper size at a glance — ISO A/B/C series plus US formats — with instant mm ⇄ inch switching and the √2 logic explained.
| Size | Width × Height | Area |
|---|
A0 = 1 m², ratio 1:√2 — each size halves the one above it. 1 in = 25.4 mm exactly.
How to use
- Scroll the table to find your paper size.
- Switch mm / in to see both metric and imperial dimensions.
- The area column shows sheet area in mm² for print cost estimates.
Frequently asked questions
Why is A4 exactly 210 × 297 mm?
ISO 216 starts at A0 with an area of one square metre and sides in the ratio 1:√2 (≈ 1.414). Each size halves the previous one by cutting along the long side, so A0 folded once gives A1, and so on down to A10 — the ratio never changes.
Why does the 1:√2 ratio matter?
Because it lets paper scale without distortion: an A4 page enlarged onto A3 keeps the same proportions, and two A4 sheets side by side exactly match an A3. No other fixed ratio preserves this from size to size.
What is the difference between B and C series?
B series fills the gaps between A sizes with slightly larger sheets, used for books and posters. C series sizes sit between the two and are designed as envelopes: a C4 envelope takes A4 paper flat, and a C6 envelope takes A4 folded twice.
Is US Letter the same as A4?
No. Letter is 215.9 × 279.4 mm (8.5 × 11 in) — wider and shorter than A4. Documents set for one size print with shifted margins on the other, which is why international correspondence still trips people up.
How do I switch between mm and inches?
Use the unit dropdown above the table. Every width and height is converted instantly — the mm values are the ISO-defined integers, and inches are derived at exactly 25.4 mm per inch.