Percentage Change Calculator
Percentage change is the universal way to describe growth or decline: revenue versus last year, a stock versus its purchase price, a score versus last term. Enter the old and new values — this calculator returns the signed change so you can see direction and size at once.
Results
Formula
How to use this calculator
- Enter the old (starting) value.
- Enter the new value.
- Press Calculate — the signed percent change shows whether it went up or down.
Worked example
Monthly visitors grow from 75 to 90.
- Change: 90 − 75 = 15.
- Divide by the old value: 15 ÷ 75 = 0.20.
- Multiply by 100: +20%.
Result: That is a 20% increase.
Frequently asked questions
What does a negative percentage change mean?
The new value is smaller than the old one — a decrease. The size of the number tells you how large the drop was relative to the starting value.
Why can’t percentage change start from zero?
The formula divides by the old value. Division by zero is undefined, so growth from zero is described in absolute terms instead.
How do I reverse a percentage change?
To undo a change of P%, divide the new value by (1 + P/100). To reverse a decrease, divide by (1 − P/100).
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