Paper Size Converter
Convert paper sizes between millimetres, centimetres, inches and points, or identify a custom sheet.
What is Paper Sizes?
Paper sizes are a small minefield of competing standards. ISO 216 defines the A-series from first principles — A0 is one square metre and each step halves the area, giving the 1:√2 ratio that makes A4 and A3 the same shape — while North American sizes are inch dimensions with their own names, so Letter is 8.5 × 11 in and therefore 215.9 × 279.4 mm rather than any round figure. Print dialogs, printer trays and paper merchants each tend to speak one of the two, and the conversions are not memorable.
How it works
Every size is stored in millimetres, the canonical unit, and converted on output, so a size cannot be rounded twice. Custom dimensions are treated the same way: they are converted to millimetres, compared with the ISO A-series within a tolerance of a millimetre and a half, and named if they match — which is how a measured sheet is identified as A4 or as something that only looks like it. A comparison against A4 and Letter gives the scale factors for a print dialog, and the whole table is rendered in the chosen unit so switching to inches converts every row at once.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.