A traditional Japanese unit of length, roughly the distance from the tip of the thumb to the tip of the little finger when the hand is spread. Rare in modern usage; mainly encountered in historical or traditional contexts.
In old Japan, one span was considered to be about 18 centimeters.
Compound of 一指 (one finger) and 当たり (per, about). The exact historical derivation is uncertain, but the term literally describes the span of one hand.