noun
B5 paper size (182 mm x 257 mm)
Standard paper size used in notebooks, textbooks, and printing.
このノートはＢ５判です。
This notebook is B5 size.
Ｂ５判の用紙に印刷してください。
Please print on B5 size paper.
A4 is the most common office paper size (210 mm × 297 mm), slightly larger than B5.
B4 is larger than B5 (257 mm × 364 mm), often used for newspapers and posters.
From the B-series paper size standard (ISO 216) combined with 判 (はん, 'size').