paper sizes in Japan

Japan has adopted the ISO series A sizes, but its series B sizes are slightly different.¹ These sizes are sometimes called JIS B or JB sizes.

A JB0 sheet has an area of 1.5 square meters. The area of each size is the arithmetic average of the areas of the A series page with the same number and the A series page with the next higher number. So for example, the area of a JB4 page is the average of the area of an A4 sheet and an A5 sheet. (In the ISO B series, the area of each sheet is the geometric mean of the A sizes, that is, the square root of the sum of their areas.)

JB0	1030 mm × 1456 mm
JB1	728 mm × 1030 mm
JB2	515 mm × 728 mm
JB3	364 mm × 515 mm
JB4	257 mm × 364 mm
JB5	182 mm × 257 mm
JB6	128 mm × 182 mm
JB7	91 mm × 128 mm
JB8	64 mm × 91 mm
JB9	45 mm × 64 mm
JB10	32 mm × 45 mm

1. JIS P 0138-61

Traditional paper sizes

shiroku-ban

base size: 788 mm by 1091 mm (26 sun × 36 sun)

4 × 6/4 264 by 379 ( × 12.5 sun)

4 × 6/5 191 by 259 (printing on half sheets)

4 × 6/5 189 by 262

kiku-ban

base size: 639 mm × 939 mm (21 sun × 31 sun)

Kiku 4, 227 mm × 306 mm

Kiku 5, 151 mm × 227 mm