Japanese B-Series Poster Sizes Explained: B1 to B5, and Why B5 Isn't A4
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Japanese posters and chirashi are sized to the JIS B-series, not the international ISO series most people know from office paper. The two look similar on paper but aren't the same, which is why "is B5 the same as A4?" doesn't have a straightforward yes.
Japanese B-series sizes (B0–B6)
| Size | Millimetres | Inches | Typical use |
|---|---|---|---|
| B0 | 1030 × 1456 mm | 40.6" × 57.3" | Large-format theatrical posters |
| B1 | 728 × 1030 mm | 28.7" × 40.6" | Standard Japanese cinema poster |
| B2 | 515 × 728 mm | 20.3" × 28.7" | Mid-size promotional posters |
| B3 | 364 × 515 mm | 14.3" × 20.3" | Smaller display posters |
| B4 | 257 × 364 mm | 10.1" × 14.3" | Programme sheets, larger flyers |
| B5 | 182 × 257 mm | 7.2" × 10.1" | Chirashi handbills |
| B6 | 128 × 182 mm | 5.0" × 7.2" | Mini flyers, postcards |
B1 is the size most people mean by a "Japanese movie poster" — the format used for lobby and street displays. B5 is the chirashi size: small enough to hand out or slip into a bag, big enough to carry full artwork.
Is B5 equal to A4?
No. A4 (210 × 297 mm) is larger than JIS B5 (182 × 257 mm) in both directions — roughly 28mm wider and 40mm taller. A B5 chirashi will sit inside an A4 sheet with a visible border all round; it won't fill an A4 frame or sleeve.
The confusion comes from the naming. Japan's B-series isn't built the same way as the ISO B-series used in Europe (the standard behind ISO B5, which is 176 × 250 mm — close to, but still not, JIS B5). JIS B sizes are scaled at 1.5× the area of the matching A-series sheet; ISO B sizes are scaled at √2×. Different formula, different numbers, even though the names match.
In short: A4 ≠ JIS B5 ≠ ISO B5. Three different sizes, three different names that sound interchangeable.
Why chirashi are B5
B5 became the standard for Japanese cinema handbills because it hits a practical middle ground — large enough for a full poster-style layout, small enough to produce and distribute cheaply in volume for every release. It's also why chirashi collections are so compact to store compared with full B1 posters.
Framing a B5 chirashi
Because B5 doesn't match A4, standard A4 frames leave a noticeable gap. For a clean fit, look for:
- A frame sized specifically to 182 × 257 mm (sold as "B5" by some framers)
- A slightly oversized mount with a B5 aperture cut into it, if you want an A-series frame for consistency with other pieces
- Rigid backing board rather than adhesive mounting, since chirashi paper stock is thinner than a standard poster print