Paper Size Reference & Calculator
Complete paper size reference for designers, printers, and anyone who works with paper. Convert paper dimensions to pixels for digital projects.
Quick Answer
A4 = 210 × 297 mm (8.27 × 11.69 in). At 300 DPI = 2480 × 3508 px.
US Letter = 8.5 × 11 in (216 × 279 mm). Letter is wider, A4 is taller.
Common Paper Sizes at a Glance
| Size | mm | inches | px (300 DPI) | Common Use |
|---|---|---|---|---|
| A0 | 841 × 1189 | 33.1 × 46.8 | 9933 × 14043 | Large posters, technical drawings |
| A3 | 297 × 420 | 11.7 × 16.5 | 3508 × 4961 | Small posters, diagrams |
| A4 | 210 × 297 | 8.27 × 11.69 | 2480 × 3508 | Documents, printing |
| A5 | 148 × 210 | 5.83 × 8.27 | 1748 × 2480 | Notebooks, flyers |
| Letter | 216 × 279 | 8.5 × 11 | 2550 × 3300 | US standard documents |
| Legal | 216 × 356 | 8.5 × 14 | 2550 × 4200 | Legal documents |
| Tabloid | 279 × 432 | 11 × 17 | 3300 × 5100 | Newspapers, large prints |
Paper Size Tools
About PaperPixels
PaperPixels is your complete reference for paper sizes worldwide. Whether you are a graphic designer needing pixel dimensions, a printer checking paper specifications, or a student learning about ISO paper sizes, we have the information you need.
What You Will Find
- ISO A Series: The most common paper sizes worldwide (A0-A10)
- ISO B Series: Used for posters, books, and passports (B0-B10)
- ISO C Series: Envelope sizes designed for A series paper (C0-C10)
- North American: Letter, Legal, and Tabloid sizes
- Paper to Pixels: Convert any paper size to pixel dimensions at any DPI
What Are Standard Paper Sizes?
Paper sizes are standardized dimensions used worldwide for printing, writing, and packaging. The most widely adopted standard is ISO 216, which defines the A, B, and C series based on a consistent aspect ratio of 1 to the square root of 2 (approximately 1:1.414). This ratio has a unique property: when you fold a sheet in half along its longer side, the resulting half-sheet retains the same aspect ratio. A0 starts at one square metre of area (841 x 1189 mm), and each subsequent size (A1, A2, A3, A4, and so on) is exactly half the area of the previous one.
North America uses a different system. The US Letter size (8.5 x 11 inches or 216 x 279 mm) is the default for everyday documents, while Legal (8.5 x 14 inches) is used for contracts and legal filings. Tabloid (11 x 17 inches) serves newspapers, oversized spreadsheets, and small posters. These sizes are not based on a mathematical ratio, which means scaling between them is less predictable than in the ISO system. When sending documents internationally, the Letter-versus-A4 difference is the most common source of formatting problems.
For digital designers, knowing paper dimensions in pixels is essential for creating print-ready files. The pixel count depends on the DPI (dots per inch) setting: an A4 page at 72 DPI is 595 x 842 pixels (screen preview), while the same page at 300 DPI is 2480 x 3508 pixels (print quality). PaperPixels provides a Paper to Pixels calculator that converts any paper size to exact pixel dimensions at any DPI you specify, eliminating guesswork when setting up design files in Photoshop, Figma, or Illustrator.
Frequently Asked Questions
What is the difference between A4 and US Letter?
A4 measures 210 x 297 mm (8.27 x 11.69 inches), while US Letter measures 215.9 x 279.4 mm (8.5 x 11 inches). Letter is slightly wider and shorter. This difference causes margin and layout shifts when printing a document designed for one size on the other. Most printers can handle both, but the content may be cropped or scaled if the page size does not match.
How many pixels is A4 at 300 DPI?
At 300 DPI, an A4 sheet is 2480 x 3508 pixels. At 150 DPI it is 1240 x 1754 pixels, and at 72 DPI (screen resolution) it is 595 x 842 pixels. Use 300 DPI for professional print, 150 DPI for draft prints, and 72 DPI for on-screen previews.
Why does the ISO system use a 1:sqrt(2) ratio?
The 1:sqrt(2) ratio (approximately 1:1.414) ensures that halving a sheet along its long side produces a smaller sheet with exactly the same proportions. This means content designed for A3 can be scaled to A4 without distortion, and two A4 pages side by side equal one A3 page. The ratio was proposed by German scientist Georg Lichtenberg in 1786 and formalized in DIN 476 in 1922, later adopted as ISO 216.
What paper size should I use for posters?
Common poster sizes depend on the display context. For indoor posters, A2 (420 x 594 mm) and A1 (594 x 841 mm) are standard in ISO countries. In North America, 18 x 24 inches and 24 x 36 inches are the most common. For movie posters, the US one-sheet standard is 27 x 40 inches. PaperPixels has a dedicated Poster Size Guide with dimensions for all standard formats.
What is the C series used for?
The C series defines envelope sizes designed to fit A series paper. A C4 envelope holds an unfolded A4 sheet, a C5 envelope holds an A4 sheet folded once, and a C6 envelope holds an A4 sheet folded twice. Each C size is geometrically between the corresponding A and B sizes, ensuring a snug but insertable fit.