百（hecto）是一个国际单位制词头，表示因数100，符号为h。英语hecto源自希腊语ἑκατόν（hekaton），意为“一百”。

该词头使用较少，常见的特定应用情况有：

Hecto or hecta is a decimal unit prefix in the metric system denoting a factor of one hundred. It was adopted as a multiplier in 1795, and comes from the Greek ἑκατόν hekaton, meaning "hundred". Based on a proposal by Thomas Young, the prefix was often alternatively spelled hecato- in early 19th century sources. Its unit symbol as an SI prefix in the International System of Units (SI) is the lower case letter h.