The quick version
A4 is 210 × 297 mm — the standard sheet in every UK printer. A3 is exactly twice the area of A4 (297 × 420 mm). Fold an A3 along its long edge and you get two A4 pages. That's why booklets often start life as A3.
When A4 is the right answer
A4 is correct for almost all office documents: reports, CVs, invoices, revision notes, contracts, handouts. Anything you'd expect to file in a folder or post in an envelope is A4. It's cheaper, quicker to print, and fits every filing system.
When A3 earns its keep
- Spreadsheets with 15+ columns
- Floor plans and architectural drawings
- Shop-window notices and event posters
- Exam revision maps and children's project boards
- Photographs and artwork — A3 colour prints look genuinely impressive
Cost and practical notes
An A3 sheet uses roughly twice the ink and toner of A4 and takes a little longer to print, so costs more per page. If you only need A3 for the cover or one key page, mix sizes — most customers don't realise we can do that.
In short
Default to A4 unless the content genuinely needs more room. Bring a USB stick or email the file ahead and we'll test-print a single sheet before the full run.
Published 15 April 2026 by the Copy Shop Putney team. Shop 395-A, Tildesley Rd, Putney Heath, London SW15 3BD.