100fold

100-fold is an expression used to describe an increase or multiplier of 100 in a quantity. It indicates that the new value is 100 times the original value. In mathematical notation, a value V becomes 100V; in words, a hundredfold increase. The term is used across disciplines where ratios and fold changes are common, including biology, economics, and statistics, as well as in everyday language.

In biology and genetics, fold change describes how much a measurement has changed, such as gene expression or protein abundance. A 100-fold change means expression is 100 times higher (or lower, if it is a 100-fold decrease). In mathematics and data analysis, 'fold' is used in phrases like twofold, tenfold, or hundredfold to express multiplicative factors.

The usage implies a substantial change and, when converting to percent, a 100-fold increase corresponds to a 9,900 percent rise (assuming a nonzero baseline). If the baseline is zero, the concept of fold change is not defined.

The term also appears in branding or project names as a proper noun, but such uses are context-specific and not inherent to the mathematical meaning. Without context, '100fold' should be interpreted as a multiplier rather than a percentage. Related concepts include fold change, multiplier, and the general idea of scaling by factors of 10, 100, or higher.