Paper sizes and margins
Paper sizes and margins, in millimetres
Three paper sizes cover almost every document anybody is asked for, and they are not interchangeable. Here is what each one is, what a margin costs, and which placement setting to leave alone.
The three sizes, side by side
| Size | Millimetres | Inches | Where it is asked for |
|---|---|---|---|
| A4 | 210 × 297 | 8.27 × 11.69 | Almost everywhere outside North America |
| Letter | 215.9 × 279.4 | 8.5 × 11 | The United States and Canada |
| Legal | 215.9 × 355.6 | 8.5 × 14 | Contracts, affidavits, long forms |
Letter is 6 mm wider than A4 and 18 mm shorter. That sounds trivial and is not: a document laid out for A4 and printed on Letter loses 18 mm off the bottom or is shrunk to fit, and the shrinking is what moves a signature away from the line it was meant to sit on. Legal is Letter with another 76 mm of height and nothing else changed.
What a margin takes away
A margin is white space measured inwards from each edge. The figures below are for A4; the proportions hold for the others.
| Margin | Box left for the photograph | Share of the sheet |
|---|---|---|
| None | 210 × 297 mm | 100% |
| 10 mm | 190 × 277 mm | 84% |
| 20 mm | 170 × 257 mm | 70% |
| 25.4 mm (1 inch) | 159 × 246 mm | 63% |
Three things are worth knowing before choosing. Almost no office printer can put ink within 5 mm of the paper edge, so a document with no margin will be clipped or scaled by the print dialogue. A page that will be stapled or punched wants more on the left than elsewhere, which is what the four separate fields are for. And a bigger margin means a smaller photograph, which means fewer pixels needed to reach any given resolution — a 20 mm margin is a modest saving on the file size as well as a tidier page.
Fit against fill, and why the default is what it is
A photograph and a sheet of paper are rarely the same shape. A phone camera gives roughly 4:3; A4 is roughly 1:1.41. Something has to give, and there are only two honest answers.
Fit puts the whole photograph inside the box and leaves white where the shapes disagree. Nothing is lost and the bars are obvious. Fill makes the photograph cover the box completely and cuts off whatever hangs over the edge. It looks tidier and it is the wrong choice for a document, because what hangs over the edge of a photographed page is a line of text, a signature, or the corner with the reference number in it.
Fit is the default here for that reason. Fill is worth having for photographs that are actually photographs — a picture going onto a 4 by 6 sheet, where a few millimetres of sky is no loss.
Choosing quickly
- An Indian, European, Australian or UK form portal. A4, 20 mm margins, Fit. This is what the A4 page opens with.
- An American employer or university. Letter, 1 inch margins — switch the units to inches and type 1 into all four fields.
- A contract or a long table. Legal, portrait, 15 mm. The extra 76 mm of height is the entire point of the size.
- Photographs that are photographs. 4 by 6 inches, no margin, Fill.