What it is
Japanese wasai sun is 1 sun = 1/33 m ≈ 3.030 cm ≈ 1.193 in. Not Chinese market cun (1/30 m ≈ 1.312 in), not button ligne (1/40 in).
How to use
sun × 1.193 = inches (exact: (1/33) / 0.0254). 1 sun ≈ 1.193 in. The converter above uses this factor.
in = 寸 × 1.193032689
Example: 1 寸 = 1.193032689 in
Common uses
Kimono, yukata, and wasai drafts vs inch patterns. Confirm wasai sun vs Chinese cun before measuring.
Conversion tips
1 wasai sun ≈ 1.19 in; 1 Chinese cun ≈ 1.31 in. 40 ligne = 1 inch. Do not mix the three.