寸すん分ぶんの狂くるいもない

expression, i-adjective

perfectly accurate; flawless; without the slightest deviation

Emphasizes absolute precision or flawlessness, often used for plans, timing, measurements, or execution. The phrase 寸分 (a tiny amount) plus 狂いもない (no error) conveys that not even the smallest mistake exists.

See also: 寸分 (すんぶん)

• 彼かれの計けい算さんは寸すん分ぶんの狂くるいもない。

  His calculations are perfectly accurate.

• この時計とけいは寸すん分ぶんの狂くるいもなく動うごいている。

  This clock runs without the slightest deviation.