Normally, percentages and ratios are related by the following formula.
| percent | |
= | |
100 | * | ratio |
However, when you are comparing the value of something before and after a change the above formula is not used. The ratio is computed as usual:
| value after change | |||||
| improvement ratio | |
= | |
|
|
| value before change |
On the other hand, the improvement percentage is given by:
| improvement percent | |
= | |
100 | * | (improvement ratio | |
- | |
1) |
This formula should also be used when you are looking for a percent change or a percent increase. The above formula can also be solved to compute an improvement ratio given an improvement percent.
| improvement ratio | |
= | |
improvement percent/100 | |
+ | |
1 |