Paper Size Calculator
Exact paper dimensions in mm, cm, inches and pixels at any DPI: A4 at 300 DPI is 2480 × 3508 px. Covers A0–A8, B4–B5, C4–C6, DL, US Letter, Legal, Tabloid and Mexican oficio.
How it works
pixels = millimetres ÷ 25.4 × DPI (rounded) · inches = mm ÷ 25.4 · ISO 216: A0 = 1 m² with sides in ratio 1 : √2, and each next size halves the long side (A4 = 210 × 297 mm)
ISO 216 A sizes keep the ratio 1 : √2 (≈ 1 : 1.414), so folding a sheet in half gives the next size with the same shape; A0 has an area of one square metre. B sizes are the geometric means between A sizes and C sizes are the matching envelopes (an A4 sheet fits flat in a C4 envelope). North America uses inch-based Letter, Legal and Tabloid instead (ANSI/ASME Y14.1), and Mexico’s “oficio” is 216 × 340 mm. To get a pixel size, convert to inches and multiply by the DPI.
Worked example
A4 portrait is 210 × 297 mm = 8.27 × 11.69 inches. At 300 DPI: 210 ÷ 25.4 × 300 = 2,480.3 → 2480 px and 297 ÷ 25.4 × 300 = 3,507.9 → 3508 px, so the sheet is 2480 × 3508 px (8.70 megapixels), with aspect ratio 1 : 1.414.
Sources: ISO 216 — Writing paper and certain classes of printed matter · Paper size (Wikipedia)
Frequently asked questions
What is the size of A4 in pixels?
It depends on the resolution: 2480 × 3508 px at 300 DPI, 1240 × 1754 px at 150 DPI and 794 × 1123 px at 96 DPI (the screen/CSS standard).
What are the dimensions of A4 in cm and inches?
21 × 29.7 cm, or 8.27 × 11.69 inches. US Letter is slightly wider and shorter: 21.59 × 27.94 cm (8.5 × 11 in).
Why do A sizes have the ratio 1 : 1.414?
It is 1 : √2, the only ratio that stays the same when a sheet is folded in half. That lets you enlarge or reduce A4 to A3 or A5 on a copier without cropping.
What DPI should I use for printing?
300 DPI is the usual target for photos and print shops; 150 DPI is fine for large posters viewed from a distance; 72–96 DPI is only for screens.
What is oficio size?
In Mexico, oficio paper is 216 × 340 mm. In several other Latin American countries “oficio” means a sheet the size of US Legal (216 × 356 mm), so check locally.
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This calculator is for educational purposes. Double-check important results before acting on them.