One hundred (100) is the natural number following ninety-nine and preceding one hundred one. In scientific notation, it is written as 102. The standard SI prefix for a hundred is "hecto-". The Roman numeral for hundred is C (for centum). This number is important as the basis of percentages (literally "per hundred"), with 100% being a full amount. It is used in many physical units.

See also: List of numbers, Hundred (division), century, the year AD 100