Percentages
Percentage change calculator
Compare an original value with a new value to find the percentage increase or decrease, using the original as your baseline.
How to calculate it
Percentage change measures a difference relative to the starting amount. Moving from 80 to 100 adds 20. Because 20 is a quarter of 80, that is a 25% increase. A negative result represents a decrease. This single tool works as both a percentage increase calculator and a percentage decrease calculator: a positive result is an increase, a negative result is a decrease.
Worked examples
| Example | Working | Answer |
|---|---|---|
| 80 to 100 | (100 − 80) ÷ 80 × 100 | 25% |
| 100 to 80 | (80 − 100) ÷ 100 × 100 | −20% |
| 50 to 50 | (50 − 50) ÷ 50 × 100 | 0% |
| 200 to 250 | (250 − 200) ÷ 200 × 100 | 25% |
Frequently asked questions
Why can’t I start from zero?
The formula divides by the original value. Division by zero is undefined, so a percentage change from zero cannot be calculated with this formula.
Is percentage change the same as percentage points?
No. A rate moving from 10% to 15% rises by 5 percentage points, but by 50% relative to the original rate.
Can the original value be negative?
This tool requires a positive original value. Negative baselines can produce counterintuitive signs and need a context-specific interpretation.
Method: standard arithmetic. Examples are illustrative. How our calculators work.