B series paper sizes: B0 to B10
ISO B5 is 176 × 250 mm; JIS B5 is 182 × 257 mm. Full B0 to B10 table below.
ISO B series (B0 to B10)
The B series sits halfway between neighbouring A sizes. B0 is exactly 1 metre wide (1000 × 1414 mm), and each size down is the previous one cut in half across its longer side, rounded down to the whole millimetre. That gives the same 1 : 1.414 sheet shape as A4. A B-size sheet is the geometric mean of the A size of the same number and the one above it: B5 (176 × 250 mm) is between A4 and A5, so a B5 notebook is slightly wider and taller than an A5 notebook but narrower than an A4 one.
| Size | Millimetres | Centimetres | Inches | Area |
|---|---|---|---|---|
| B0 | 1000 × 1414 mm | 100 × 141.4 cm | 39.37 × 55.67 in | 1.414 m² |
| B1 | 707 × 1000 mm | 70.7 × 100 cm | 27.83 × 39.37 in | 0.707 m² |
| B2 | 500 × 707 mm | 50 × 70.7 cm | 19.69 × 27.83 in | 0.3535 m² |
| B3 | 353 × 500 mm | 35.3 × 50 cm | 13.9 × 19.69 in | 0.1765 m² |
| B4 | 250 × 353 mm | 25 × 35.3 cm | 9.84 × 13.9 in | 0.0882 m² |
| B5 | 176 × 250 mm | 17.6 × 25 cm | 6.93 × 9.84 in | 0.044 m² |
| B6 | 125 × 176 mm | 12.5 × 17.6 cm | 4.92 × 6.93 in | 0.022 m² |
| B7 | 88 × 125 mm | 8.8 × 12.5 cm | 3.46 × 4.92 in | 0.011 m² |
| B8 | 62 × 88 mm | 6.2 × 8.8 cm | 2.44 × 3.46 in | 0.0055 m² |
| B9 | 44 × 62 mm | 4.4 × 6.2 cm | 1.73 × 2.44 in | 0.0027 m² |
| B10 | 31 × 44 mm | 3.1 × 4.4 cm | 1.22 × 1.73 in | 0.0014 m² |
Computed from the ISO 216 construction rule and checked against the published table on Wikipedia's Paper size article. Last checked 27 October 2026.
JIS B series is not the same
Japan's standard JIS P 0138 uses the same shape but a larger area for B sizes: a JIS B sheet has 1.5 times the area of the A sheet with the same number, where an ISO B sheet is 1.414 times. So B4 and B5 bought in Japan, or in China and Taiwan where JIS B is common, are bigger than the ISO sizes. If a printer or notebook says B5 and does not say which, check the millimetres.
| Size | ISO B | JIS B | JIS is larger by |
|---|---|---|---|
| B0 | 1000 × 1414 mm | 1030 × 1456 mm | +30 × +42 mm |
| B1 | 707 × 1000 mm | 728 × 1030 mm | +21 × +30 mm |
| B2 | 500 × 707 mm | 515 × 728 mm | +15 × +21 mm |
| B3 | 353 × 500 mm | 364 × 515 mm | +11 × +15 mm |
| B4 | 250 × 353 mm | 257 × 364 mm | +7 × +11 mm |
| B5 | 176 × 250 mm | 182 × 257 mm | +6 × +7 mm |
| B6 | 125 × 176 mm | 128 × 182 mm | +3 × +6 mm |
| B7 | 88 × 125 mm | 91 × 128 mm | +3 × +3 mm |
| B8 | 62 × 88 mm | 64 × 91 mm | +2 × +3 mm |
| B9 | 44 × 62 mm | 45 × 64 mm | +1 × +2 mm |
| B10 | 31 × 44 mm | 32 × 45 mm | +1 × +1 mm |
The JIS B5 is 182 × 257 mm and the ISO B5 is 176 × 250 mm. CSS also supports JIS-B4 and JIS-B5 as named page sizes, separately from ISO B4 and B5.
What B sizes are used for
The B series is used for items that need to sit between two A sizes: books, posters, notebooks, and envelopes that hold A-size items (a B6 envelope, 125 × 176 mm, holds an A6 card with room to spare). The ID-3 passport booklet is B7 (88 × 125 mm).
The A series pages are on the paper sizes page, with single-size pages for A4 and A5. The envelopes designed to hold each size are on envelope sizes.
Frequently asked questions
What size is B5 in mm?
ISO B5 is 176 x 250 mm (6.93 x 9.84 in). JIS B5, used in Japan, is 182 x 257 mm.
What size is B4 in mm?
ISO B4 is 250 x 353 mm. JIS B4 is 257 x 364 mm.
Is B5 bigger than A5?
Yes. B5 (176 x 250 mm) is larger than A5 (148 x 210 mm) and smaller than A4 (210 x 297 mm).
What size is B0?
B0 is 1000 x 1414 mm: exactly one metre wide, and the long side is the width times the square root of two, rounded to the millimetre.
Which envelope fits B5?
A B5 sheet (176 x 250 mm) will not go in a C5 envelope (162 x 229 mm). It fits a C4 envelope (229 x 324 mm) flat, or a B5 envelope itself.