A4 vs A3 paper size: dimensions and when to use each
Updated 31 October 2026
Quick answer: A4 paper is 210 × 297 mm, the standard size for documents. A3 is 297 × 420 mm, exactly twice the area of A4, and is used for drawings, charts and small posters. On PrintPDFOnline, A3 costs twice the A4 price per page: ₹4 in black & white and ₹16 in colour.
Paper sizes at a glance
| Size | Millimetres | Inches | Typical use |
|---|---|---|---|
| A4 | 210 × 297 | 8.3 × 11.7 | Letters, notes, reports, forms |
| A3 | 297 × 420 | 11.7 × 16.5 | Drawings, charts, plans, posters |
How the A sizes relate
Each A size is half of the one before it. Fold an A3 sheet in half and you get two A4 sheets. That is why an A4 PDF printed on A3 is enlarged by about 141% on each side.
When to use A4
Almost everything: assignments, notes, reports, letters and forms. It is cheaper, easier to bind and fits standard files and folders.
When to use A3
Engineering and architecture drawings, wide spreadsheets, timelines, mind maps and small posters, anywhere detail matters or A4 would make the text too small.
Ready to print? Choose A3 printing or standard A4 when you upload your PDF.