B series paper sizes: B0 to B10
The ISO B series starts at B0 with 1000 × 1414 mm. Every B size sits between two A sizes: B4 (250 × 353 mm) is bigger than A4 and smaller than A3. B sizes are mainly used for padded envelopes, posters and books.
Contents of this page
All B sizes with dimensions
| Size | mm | cm | inches | Pixels at 300 dpi |
|---|---|---|---|---|
| B0 | 1000 × 1414 mm | 100 × 141.4 cm | 39.37 × 55.67 in | 11,811 × 16,701 px |
| B1 | 707 × 1000 mm | 70.7 × 100 cm | 27.83 × 39.37 in | 8350 × 11,811 px |
| B2 | 500 × 707 mm | 50 × 70.7 cm | 19.69 × 27.83 in | 5906 × 8350 px |
| B3 | 353 × 500 mm | 35.3 × 50 cm | 13.9 × 19.69 in | 4169 × 5906 px |
| B4 | 250 × 353 mm | 25 × 35.3 cm | 9.84 × 13.9 in | 2953 × 4169 px |
| B5 | 176 × 250 mm | 17.6 × 25 cm | 6.93 × 9.84 in | 2079 × 2953 px |
| B6 | 125 × 176 mm | 12.5 × 17.6 cm | 4.92 × 6.93 in | 1476 × 2079 px |
| B7 | 88 × 125 mm | 8.8 × 12.5 cm | 3.46 × 4.92 in | 1039 × 1476 px |
| B8 | 62 × 88 mm | 6.2 × 8.8 cm | 2.44 × 3.46 in | 732 × 1039 px |
| B9 | 44 × 62 mm | 4.4 × 6.2 cm | 1.73 × 2.44 in | 520 × 732 px |
| B10 | 31 × 44 mm | 3.1 × 4.4 cm | 1.22 × 1.73 in | 366 × 520 px |
How the B series is calculated
B0 is defined so that its short side is exactly one metre. With the 1 to √2 ratio, the long side comes to 1414 mm. Every smaller B size is made by halving, just like the A series.
Mathematically each B size is the geometric mean of two neighbouring A sizes. So B4 sits exactly “between” A4 and A3: each side of B4 is 1.19 times the A4 side (the fourth root of 2). That is useful whenever you need to wrap an A size with a little margin, for instance with an envelope or a book cover.
What B sizes are used for
| Size | Typical use |
|---|---|
| B1 | Posters, large art prints |
| B2 | Posters, sheets for smaller offset presses |
| B4 | Padded envelopes for thick A4 documents or a whole C4 envelope |
| B5 | Envelopes for A5 booklets, books, notebooks |
| B6 | Paperbacks, envelopes for C6 |
| B7 | Passports (ID-3 card format, 125 × 88 mm) |
| B8 | Playing cards, small cards |
Posters often use 70 × 100 cm. That is not B1, even though it is close (B1 is 70.7 × 100 cm). 70 × 100 cm is a classic press sheet size.
Watch out: Japanese B5 is bigger
Japan has its own B series under the JIS standard, with sides about 3 % longer. JIS B5 measures 182 × 257 mm, while ISO B5 is 176 × 250 mm. Printers and copiers from Japanese brands often offer both, and the menu sometimes just says “B5”. If a print on B5 paper looks shifted, that is usually the reason. All dimensions are on the international sizes page.
Frequently asked questions
How big is B4?
B4 measures 250 × 353 mm, slightly larger than C4 (229 × 324 mm), so a C4 envelope fits into a B4 envelope.
How big is B5?
ISO B5 is 176 × 250 mm. The Japanese JIS B5 is a little larger at 182 × 257 mm.
Is B5 bigger than A5?
Yes. B5 sits between A5 (148 × 210 mm) and A4 (210 × 297 mm).
What are B sizes used for?
Mainly padded envelopes, posters, books and passports. A B envelope takes a C envelope of the same number.