公丈（（英式英文：decametre、美式英文：decameter））或又称十米，是公制的长度单位，1公丈=10米=0.01公里，该长度单位在实际上的使用很少，少数的使用如在水文学中，测量重力位高度的工具。

A decametre or dekametre (American spelling: dekameter, earlier decameter; symbol dam, sometimes unofficially Dm or dkm) is a very rarely used unit of length in the metric system, equal to ten metres, the SI base unit of length. It can be written in scientific notation as 7001100000000000000♠1×10 m or 1 E+1 m (exponential notation), meaning 1 × 10 m.