How to measure a sheet
Measure the short edge first, then the long edge, in millimetres if you can. A steel ruler against the edge is fine; a tape measure sags. If you only have inches, that is fine too, the finder converts.
Type both numbers, pick the unit, and the answer appears as you type. The best match is highlighted; the list below it shows the next five closest sizes with how many millimetres they differ, so a sheet that is almost A4 is still easy to identify.
What the tolerance means
Sizes rarely measure exactly what the standard says. ISO 216 allows ±1.5 mm on sheets up to 150 mm, ±2 mm up to 600 mm and ±3 mm above that. Trimmed printed pieces can lose a further 3 mm per edge of bleed. The default tolerance of ±5 mm covers all of that; widen it for hand-cut or historical paper.
Common results
- 8.5 × 11 in is Letter (also called ANSI A).
- 210 × 297 mm is A4, the most common sheet in the world outside North America.
- 8.5 × 14 in is Legal.
- 110 × 220 mm is a DL envelope, the one an A4 letter folded in thirds fits into.
- 4 × 6 in is a 4R photo print, sold as 10 × 15 cm in Europe.