B6 paper size: ISO 125 × 176 mm and JIS 128 × 182 mm

B6 measures 12.5 × 17.6 cm under ISO and 12.8 × 18.2 cm under JIS. Both are official standards. If you are buying a planner or preparing a print file, first establish which B6 the seller or printer means.

Complete B6 dimensions

Japanese planners and stationery generally use the slightly larger JIS version; the source also describes JIS use in Japanese publishing and Taiwanese printing. The two versions differ by 3 mm on the short edge and 6 mm on the long edge—enough to matter around bleed and trim.

Why there are two standards

ISO B-series dimensions sit geometrically between adjacent A sizes: Bn uses the geometric mean of An and A(n−1). For example, the B6 short edge is 125 mm ≈ √(105 × 148). The starting areas differ: JIS B0 = 1.5 m², while ISO B0 = √2 m². This makes Japanese B sizes slightly larger. A sizes do not have this ISO/JIS split.

For a print order, state 125 × 176 mm or 128 × 182 mm rather than simply saying “B6”.

B6 compared with A5 and A6

Both B6 versions sit between A5 and A6. JIS B6 has about 25% less area than A5 and 50% more than A6; ISO B6 has about 29% less than A5 and 42% more than A6. Looking the other way, A5 is about 33% larger than JIS B6 or 41% larger than ISO B6. B6 is roomier than a postcard-sized A6 yet smaller than an A5 notebook, making it convenient for weekly plans and small bags.

flowchart TB
  A["B5"] -->|Half-fold| B["B6"]

B6 is obtained by folding B5 in half within the same standard. The diagram explains the relationship; whole-millimetre dimensions are rounded, so it is not a precision cutting instruction.

The 5×7 photo comparison

A 5×7-inch photograph converts exactly to 12.7 × 17.78 cm (often rounded to 12.7 × 17.8 cm), with an area of about 225.8 cm². It lies between the two B6 sizes: about 2.6% larger in area than ISO B6 and 3.1% smaller than JIS B6.

For a photo sleeve, check its actual internal dimensions. JIS B6 is slightly larger than the photo, but both edges of ISO B6 are shorter. The label “B6” alone does not guarantee a fit.

Uses and practical limits

• Planners and notebooks: a common Japanese planner size, generally JIS.
• Books: Japanese collected volumes and some Taiwanese literary or reference books use B6 or a nearby trim size.
• Small leaflets and menus: about 1.4–1.5 times the area of A6, while still handheld.
• Small-item storage: a JIS B6 pouch can be a candidate for 5×7 photos or passbooks, subject to its actual usable inside size.

These are source-specific examples, not a claim that every country uses the same paper convention. Confirm the manufacturer’s standard and finished dimensions.

Related: B4 sizes

Frequently asked questions

How big is B6 in centimetres?

ISO B6 is 12.5 × 17.6 cm; JIS B6 is 12.8 × 18.2 cm. Japanese planners generally use JIS.

Which is bigger, B6 or A5?

A5 is bigger. Its 14.8 × 21.0 cm area is about 33% greater than JIS B6 and 41% greater than ISO B6.

Which is bigger, B6 or A6?

B6 is bigger. Compared with A6 (10.5 × 14.8 cm), its area is approximately 42% greater for ISO or 50% greater for JIS.

How many pixels for B6 printing?

At 300 DPI, ISO B6 is 1476 × 2079 px and JIS B6 is 1512 × 2150 px. Confirm the standard with the printer.

Which standard do Japanese B6 planners use?

Generally JIS, 12.8 × 18.2 cm. Check the product’s stated dimensions rather than assuming that all B6 items use it.

Is B6 the same size as a 5×7 photo?

They are close, but not identical. A 5×7 photo is exactly 12.7 × 17.78 cm: about 2.6% larger in area than ISO B6 and 3.1% smaller than JIS B6. Check a sleeve’s internal dimensions.