A4 paper is the most widely used paper size globally, measuring 210 × 297 mm (8.27 × 11.69 inches). It is part of the ISO 216 standard, which is itself based on the German DIN 476 standard introduced in 1922. If you have ever printed a document at home or in an office, chances are you used A4.
The Genius of the √2 Aspect Ratio
What makes the A series so special is its aspect ratio of 1:√2 (approximately 1:1.4142). This means that when you cut a sheet of A0 in half, you get two sheets of A1 — each with the exact same aspect ratio. Cut A1 in half and you get A2, and so on down to A10. This property is what allows documents to be scaled up or down without distortion, and it is the reason photocopiers can fit four A4 pages on one A3 sheet or scale a poster down to a postcard.
The Full A Series
The base size, A0, has an area of exactly one square metre. Every subsequent size is half the area of the previous one:
- A0 — 841 × 1189 mm
- A1 — 594 × 841 mm
- A2 — 420 × 594 mm
- A3 — 297 × 420 mm
- A4 — 210 × 297 mm (the everyday standard)
- A5 — 148 × 210 mm (notebooks, flyers)
- A6 — 105 × 148 mm (postcards)
Why A4 Became Universal
Before ISO 216, every country had its own paper sizes. Britain had Foolscap and Quarto, the US had Letter and Legal, and France had Raisin and Aigle. This chaos made international trade and printing difficult. The ISO standard, adopted broadly after World War II, provided a single framework. A4 was the natural "default" size because it fits into briefcases, holds about 2,000 words of typed text comfortably, and can be folded to fit a C5 envelope.
Common Uses of A4
- Office documents, letters, contracts
- Academic essays and dissertations
- Magazines, brochures (folded)
- Standard printer paper worldwide
- Photocopying and scanning
A4 vs US Letter
The main alternative is US Letter (8.5 × 11 inches, or 216 × 279 mm). A4 is slightly narrower and slightly taller than Letter. This means printing A4 documents on Letter paper (or vice versa) often requires scaling to 94–97% to avoid clipping. In a globalised world, this mismatch is a constant source of minor printing headaches — but it is a reminder that even something as simple as paper size reflects deep cultural and historical differences. visit more: A4 Size Paper Sizes Papierformate
Every paper size in our database is listed with its full dimensions in mm, cm, inches, points, picas, and pixels at both 72 and 300 dpi.