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.
|% 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.