Paper size FAQ
Short answers to the questions we are asked most often. Each answer links to the page where the topic is explained in full.
Contents of this page
Sizes and dimensions
What size is A4?
A4 measures 210 × 297 mm, which is 21 × 29.7 cm or 8.27 × 11.69 inches. More on the A4 size page.
What size is A5?
A5 measures 148 × 210 mm and is exactly half an A4 sheet. See A5 size.
What size is A3?
A3 measures 297 × 420 mm, twice the size of A4. See A3 size.
What paper size series are there?
The A series for paper and printed matter, the B series for posters and mailers, and the C series for envelopes, each from 0 to 10. The former D series is no longer standardised. Overview under paper sizes.
How are A sizes calculated?
A0 has an area of one square metre and an aspect ratio of 1 to √2. Each smaller size is made by halving the long side. The formulas are under aspect ratio.
Envelopes and post
Which envelope fits A4?
Unfolded, C4. Folded once, C5. Folded twice crosswise, C6. Folded in three, DL. See envelope sizes.
What size is a postcard?
Most postcards are A6 at 105 × 148 mm. See A6 size.
What size is a business card?
In the UK and most of Europe 85 × 55 mm, in the US 3.5 × 2 inches. Business cards have nothing to do with A8 (52 × 74 mm), despite a common belief. See business card sizes.
How many sheets fit in a German standard letter?
With 80 g/m² paper and a DL envelope, two sheets are safe and the third puts you at the 20 g limit. See German letter sizes.
Print and paper
How much bleed does a print file need?
Usually 3 mm on every side, or 1/8 inch in the US. See bleed.
What resolution do I need for print?
About 300 dpi at final size. For posters, 150 dpi is often enough. See print resolution.
What percentage do I use to copy A4 to A3?
141 %. From A3 to A4, 71 %. All factors are in the scaling factor calculator.
How much does a sheet of A4 weigh?
At 80 g/m², 4.99 grams. See paper weight.
Standards and history
Who invented A4?
Walter Porstmann. The standard DIN 476 was published on 18 August 1922. The idea of the aspect ratio came from Georg Christoph Lichtenberg in 1786. See history.
Which standard defines A4 today?
ISO 216, published in the UK as BS EN ISO 216 and in Germany as DIN EN ISO 216. See standards.
Why does the US not use A4?
The US never fully adopted the metric system and still uses Letter (8.5 × 11 inches). See Letter vs A4.
Do ISO paper sizes have a 5:7 ratio?
No. The ratio is 1 to √2, about 1 to 1.414. 5 to 7 equals 1 to 1.4 and is a common misconception.
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