Paper Size Converter
Convert any standard paper size between millimetres, inches, points and pixels at a chosen resolution.
Processing: This tool runs entirely in your browser. Your input and any file you open stay on your device — nothing is uploaded to a server.
How to use the paper size converter
- Fill in the fields — they start with a worked example.
- Read the answer, and the arithmetic shown beneath it.
- Copy the results, or adjust the inputs to compare scenarios.
About this tool
The ISO A series is built on one idea: every sheet has the same 1:√2 proportions, so folding it in half gives the next size down without leaving a margin of waste. A0 is one square metre, A1 is half of it, and A4 is a sixteenth. That is why enlarging A4 artwork to A3 never changes the composition, and why a European printer can scale a job between sizes without redesigning it.
US sizes come from a different history and follow no such rule. Letter is 8.5 × 11 inches, Legal is longer but not proportionally so, and scaling between them always crops or leaves a band of white. Documents that move between the two systems are the usual source of a stray blank page at the end of a print run.
The pixel column is the one that needs care. A paper size has no native pixel dimension — it acquires one only at a chosen resolution, which is why A4 is 2480 × 3508 at 300 PPI but 794 × 1123 at 96 PPI. Set the resolution to match the job before you copy those numbers into a canvas.
Common uses
- Setting up a canvas in pixels for an A4 or Letter document at print resolution.
- Checking an unfamiliar paper size in millimetres before ordering stock.
- Converting between A-series and US sizes for a document sent abroad.
Frequently asked questions
- What is A4 in pixels?
- It depends entirely on resolution: 2480 × 3508 pixels at 300 PPI, 1240 × 1754 at 150 PPI, and 794 × 1123 at the 96 PPI browsers assume.
- Why is A4 not a round number of millimetres?
- Because the series is defined by area and proportion rather than by its edges. A0 is one square metre at a 1:√2 ratio, and every smaller size is that sheet halved, which lands on 210 × 297 mm by A4.
- Is US Letter the same as A4?
- No. Letter is wider and shorter — 216 × 279 mm against A4's 210 × 297 mm — so a document laid out for one always needs rescaling for the other.
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