How this calculator works
Calculate percentage increase or decrease between two values.. Percentage change is the difference between new and old values divided by the old value, multiplied by 100. When an amount moves from 80 to 100, the change is 20 on a base of 80, or 25%. The base matters: reversing direction does not produce the same percentage.
Important assumptions
If a rate moves from 10% to 15%, it rises by five percentage points. Relative to the starting 10%, that is a 50% increase. These statements describe different things; don't treat the phrases as interchangeable.
Common mistakes to avoid
- Mixing units or time periods.
- Counting the same fee or tax twice.
- Treating an estimate as a live quote or guarantee.
- Ignoring maintenance, waste, exceptions or other costs outside the inputs.
Read the related guide
Percentage Increase vs. Percentage Points: The Difference That Matters →
This calculator is a planning aid. Verify important amounts with the relevant provider or official source.