Percentage calculator — change, of, and what percent
Four percentage calculations in one place, each showing the formula it used so you can check the result. Nothing is pre-filled.
Runs in your browser — your input is not uploaded to ToolsNow.
The starting value.
The value after the change.
Percent change compares the new value to the original. Percent difference is not the same thing — it uses the average of the two values as its base.
How to use
- Percent change
- How much a value rose or fell. 120 → 150 is a 25% increase.
- Apply %
- Add or remove a percentage from a base. 200 with 15% gives 230 or 170.
- X% of Y
- A straight share of an amount. 12.5% of 800 = 100.
- What % is X of Y
- Turn a ratio into a percentage. 45 out of 180 = 25%.
Questions
How do I reverse a discount?
Divide by (1 − discount). An item reduced 20% to €80 was €80 ÷ 0.8 = €100 before the discount. Subtracting 20% from €80 gives the wrong answer.
Is percent change the same as percent difference?
No. Percent change measures the new value against the original. Percent difference uses the average of the two values as its base, so it gives a smaller figure and has no direction.
Why does a 50% rise followed by a 50% fall not return to the start?
Because the second percentage applies to a larger base. 100 → 150 → 75. Percentages do not cancel out; you need to divide by 1.5 to undo a 50% increase.