A centimetre (American spelling: centimeter, symbol cm) is a unit of length in the metric system, equal to one hundredth of a metre, which is the current SI base unit of length. Centi is the SI prefix for a factor of . BIPM - SI prefixes Hence a centimetre can be written as (engineering notation) or (scientific E notation) — meaning or respectively,centimetre-gram-second system of units. Though for many physical quantities, SI prefixes for factors of 103—like milli- and kilo-—a… (More on Centimetre)