The UK uses the international "A series" of paper sizes (ISO 216). The system is simple once you see the pattern: every size is exactly half the size above it, folded across the longer edge. Here is every common size in centimetres, millimetres and inches, followed by what each one is actually used for.
UK paper sizes chart
| Size | Millimetres | Centimetres | Inches |
|---|---|---|---|
| A0 | 841 × 1189 mm | 84.1 × 118.9 cm | 33.1 × 46.8 in |
| A1 | 594 × 841 mm | 59.4 × 84.1 cm | 23.4 × 33.1 in |
| A2 | 420 × 594 mm | 42 × 59.4 cm | 16.5 × 23.4 in |
| A3 | 297 × 420 mm | 29.7 × 42 cm | 11.7 × 16.5 in |
| A4 | 210 × 297 mm | 21 × 29.7 cm | 8.27 × 11.69 in |
| A5 | 148 × 210 mm | 14.8 × 21 cm | 5.83 × 8.27 in |
| A6 | 105 × 148 mm | 10.5 × 14.8 cm | 4.13 × 5.83 in |
What each paper size is used for
A4 — the everyday standard
A4 (21 × 29.7 cm) is the default for virtually every document in the UK: letters, contracts, CVs, forms, coursework, and anything you'd file in a folder. If a website or printer just says "paper", it almost always means A4. For a deeper look, see our dedicated A4 size guide.
A5 — half of A4
A5 (14.8 × 21 cm) is A4 folded in half. It's the classic size for booklets, flyers, invitations, and notepads — big enough to read comfortably, small enough to post cheaply.
A3 — double A4
A3 (29.7 × 42 cm) is two A4 sheets side by side. It suits posters, plans, spreadsheets that are unreadable at A4, artwork, and presentation displays.
A2, A1 and A0 — poster territory
Each step doubles the sheet again. A2 (42 × 59.4 cm) works for small posters and wall charts, A1 (59.4 × 84.1 cm) for event posters and academic conference posters, and A0 (84.1 × 118.9 cm) for large-format display work. These need specialist wide-format printers, which is why high-street options are limited and prices jump sharply.
A6 — postcard size
A6 (10.5 × 14.8 cm) is a quarter of A4 — the standard postcard and small flyer size.
Why the A series is clever
Every A-series sheet has the same proportions (1:√2). Halve or double any size and the shape stays identical, which is why an A4 document scales perfectly onto A5 or A3 with no awkward margins — and why photocopiers offer clean 71% and 141% scaling buttons.
UK paper sizes vs US Letter
The US uses Letter (8.5 × 11 in, roughly 216 × 279 mm) instead of A4. Letter is slightly wider and shorter than A4, so US templates printed in the UK can clip at the edges. If a document was made for Letter, set your PDF export to A4 (or choose "fit to page") before printing — our guide to saving a PDF for printing covers this.
Printing any of these sizes without a printer
Most home printers only handle A4 and A5. If you need documents printed and you don't have a printer — or you need a size yours can't take — you can upload your PDF to printle and have it printed and posted anywhere in the UK, with black & white from 15p per page and same-day dispatch on working days before 2 PM.