Compare and convert A-series, B-series, US Letter, Legal, Tabloid, and custom paper sizes.
This tool lays out standard sheet dimensions (ISO A and B series, US Letter, Legal, Tabloid) side by side in mm, cm, and inches, and lets you enter a custom width and height to see which standard size it's closest to. What trips people up most: A4 and Letter are not the same shape. Letter is 8.5 x 11 in (a 1.29:1 ratio); A4 is 210 x 297 mm (a 1:1.414 ratio, the square root of 2). A document formatted for one will not fill the other page - it either leaves a margin gap or gets clipped, which is why cross-border print jobs so often come out wrong.
A concrete input and expected output from the current implementation.
Input
A4
Expected output
210 mm x 297 mm = 21.0 cm x 29.7 cm = 8.27 in x 11.69 in
A4's fixed ISO dimensions of 210 mm by 297 mm are divided by 25.4 (the exact number of millimeters in one inch) to get 8.27 and 11.69 inches.
A-series and B-series sizes aren't independently listed constants for every entry; each size in the series is the previous one cut in half across its long edge, and the series is defined so every size keeps the same aspect ratio of 1:sqrt(2). Starting from A0 (841 x 1189 mm, an area of almost exactly 1 m2), the tool halves down to get A1 through A6, and the same rule generates the B series from B0.
All internal dimensions are stored in millimeters. Centimeter values divide by 10, and inch values divide by 25.4 - the internationally defined length of one inch since 1959. US sizes (Letter, Legal, Tabloid) are stored in inches natively and converted the other direction to get their mm and cm figures, so rounding direction differs depending on which system a size originates in.
No. They're close in area but different shapes: A4 is 210 x 297 mm (8.27 x 11.69 in), Letter is 215.9 x 279.4 mm (8.5 x 11 in). Letter is wider and shorter than A4. A file formatted for one will not print edge-to-edge correctly on the other.
No. It only compares the trimmed sheet dimensions defined by each standard. Margins, bleed, and safe-print areas depend on your printer or print shop's setup and aren't part of the paper size specification itself, so check those separately.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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