Paper Size Converter – ISO, North American, JIS & Specialty Sizes
Paper size standards differ significantly between regions. A designer in Tokyo working with JIS B5 stationery, a print shop in New York setting up US Letter templates, and a European publisher preparing A4 documents all use different measurement systems. This Paper Size Converter bridges those standards instantly, letting you look up dimensions, compare series, calculate pixel sizes for screen and print, and identify any custom width-by-height combination against a database of over 60 named sizes.
Supported Paper Size Standards
The tool covers every major international standard:
- ISO 216 A-series (A0–A10) — the global default for offices, schools, and publishing. A4 (210 × 297 mm) is used in over 160 countries.
- ISO 216 B-series (B0–B10) — slightly larger than the A equivalents, commonly used for posters, books, and passports.
- ISO 269 C-series (C0–C10) — envelope sizes designed so an A-size sheet folds neatly inside the matching C envelope. C4 holds a flat A4 sheet; C5 holds an A4 folded in half.
- North American sizes — US Letter (8.5 × 11 in), US Legal (8.5 × 14 in), Tabloid/Ledger (11 × 17 in), Executive, Statement, and ANSI A–E for engineering drawings.
- JIS B-series (JIS B0–B8) — Japan's national standard, slightly larger than ISO B sizes. JIS B5 (182 × 257 mm) is the dominant notebook size across Japan.
- Specialty and traditional sizes — Folio, Quarto, Demy, Crown, Royal, and Foolscap, still used in book publishing, legal documents, and heritage printing.
How the ISO A-Series Is Defined
The ISO A-series is based on two elegant mathematical properties. A0 has an area of exactly 1 square metre and an aspect ratio of 1 : √2 (approximately 1 : 1.41421). This ratio means that when you fold an A-series sheet in half along its longer edge, the resulting shape has the same aspect ratio — just half the area. That is why A1 is exactly half of A0, A2 is half of A1, and so on.
The precise dimensions of A0 are 841 × 1189 mm. Each subsequent size is obtained by halving the longer dimension and rounding to the nearest millimetre:
A1 = 594 × 841 mmA2 = 420 × 594 mmA4 = 210 × 297 mmA5 = 148 × 210 mm
The B-series sizes are defined as the geometric mean between consecutive A sizes. The C-series envelope sizes sit geometrically between A and B, so a C4 envelope fits an A4 sheet flat, and a C5 envelope fits an A4 sheet folded once.
Pixel Dimensions and DPI
When working in digital design, you need to know the pixel dimensions of a paper size at a given DPI (dots per inch). The formula is straightforward:
pixel_width = round(mm_width / 25.4 × DPI)
Common DPI values and their use cases:
- 72 DPI — legacy web/screen resolution (macOS point-based display)
- 96 DPI — Windows screen default; common for UI mockups
- 150 DPI — low-resolution print, newsletter-quality images
- 300 DPI — standard professional print quality
- 600 DPI — high-resolution print, fine-detail technical drawings
For example, A4 at 300 DPI is 2480 × 3508 pixels — the standard canvas size for document-quality print design.
ISO B-Series vs JIS B-Series
A common source of confusion is the difference between ISO B-series and JIS B-series sizes. They share the same letter designations but have different dimensions. ISO B5 is 176 × 250 mm, while JIS B5 is 182 × 257 mm — about 3–4% larger in each dimension. If you are ordering print-ready files for a Japanese printer or preparing notebooks for the Japanese market, always confirm which B-series the recipient uses.
Orientation: Portrait and Landscape
By convention, paper sizes are always described in portrait orientation (width < height). Selecting landscape in the converter swaps the width and height values before display, without changing the underlying standard dimensions. This is useful when you need to confirm the pixel canvas size for a wide-format layout or a landscape-oriented poster.
Custom Size Finder
If you have a document or image with specific dimensions and want to know which standard paper size it corresponds to, use the Custom Size Finder. Enter your width and height in any unit (mm, cm, inches, or pixels), and the tool ranks the five closest named sizes by area similarity. A 100 % match means the areas are identical; high scores above 90 % typically indicate a near-exact match within rounding tolerances.
Practical Uses
Graphic designers use the tool to set up document bleeds and safe-area margins when switching between US Letter and A4 templates. Print professionals verify whether their output sizes are compatible with standard sheet-fed printers. Developers creating PDF generation scripts look up exact pixel dimensions for canvas initialisation. Students and office workers check whether a document formatted for A4 will fit on US Letter paper without cutting off content — since Letter is slightly shorter (279 mm vs 297 mm) and slightly wider (216 mm vs 210 mm) than A4.