I've been asked many times, how to calculate percentage change. So here is a handy calculator for your convenience, and a permalink to any changes you make below.

Variable | Definition | Value |

Value 1 | ||

Value 2 | ||

% change, 1 → 2 | (V2 - V1) / |V1| | |

% change, 2 → 1 | (V1 - V2) / |V2| | |

% ratio, 1 : 2 | V1 / V2 | |

% ratio, 2 : 1 | V2 / V1 | |

% difference | |V1 - V2| / ((|V1| + |V2|)/2) |

One needs to be careful when interpreting or phrasing the above results.

For example, if v1 and v2 are benchmark times, one can either say that:

- performance v1 to v2, has decreased by 100%
- performance v2 to v1, has increased by 50%
- performance of v1 is 200% that of v2
- performance of v2 is 50% that of v1

The percentage difference value can be used where there is no directionality implied, and one just wants the relative difference between two values.

© Apr 8 2011