Percentage change calculator
Percentage change = (new value − old value) ÷ old value × 100. Going from 80 to 100 is a 25% increase; going from 100 to 80 is a 20% decrease.
- Checked on thousands of cases
- Updated November 1, 2026
Change
Increase
- Difference
- +20
- Multiplier
- × 1.25
Quick challenge
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Test yourself: every answer is computed by the tool, and the wrong choices are the most common traps.
How it works
Formula: Change (%) = (new − old) ÷ |old| × 100
Subtract the old value from the new one, divide by the old value, then multiply by 100. A positive result is an increase, a negative result a decrease. The multiplier (new ÷ old) gives the same information: 1.25 means +25%, 0.8 means −20%. The change is always measured against the starting value, which is why the change from 80 to 100 and from 100 to 80 are not the same percentage.
Worked examples
A price goes from 80 to 100
(100 − 80) ÷ 80 × 100 = +25%.
A price goes from 100 to 80
(80 − 100) ÷ 100 × 100 = −20%.
A salary goes from 2,000 to 2,100
A 5% raise.
Common mistakes
Dividing by the new value: (100 − 80) ÷ 100 = 20%.
Always divide by the starting value: +25%.
Thinking a 25% rise is undone by a 25% fall.
From 100, it takes a 20% fall to get back to 80.
Mixing up points and percent: from 10% to 12%, "+2%".
That is +2 points, a 20% increase.
Percentage change examples
| Old value | New value | Change |
|---|---|---|
| 50 | 60 | +20% |
| 80 | 100 | +25% |
| 100 | 80 | -20% |
| 100 | 150 | +50% |
| 200 | 150 | -25% |
| 40 | 100 | +150% |
| 1,000 | 1,050 | +5% |
| 250 | 200 | -20% |
Frequently asked questions
How do I calculate a percentage increase?
Divide the increase by the starting value and multiply by 100. From 50 to 65: (65 − 50) ÷ 50 × 100 = 30% increase.
How do I calculate a percentage decrease?
Same formula; the result is negative. From 200 to 150: (150 − 200) ÷ 200 × 100 = −25%, a 25% decrease.
Why can't the starting value be zero?
The change is a ratio to the starting value, and you cannot divide by zero. Going from 0 to 10 is an increase of 10, but it has no percentage.
What is the difference between percent and percentage points?
If a rate goes from 10% to 12%, it rose by 2 percentage points, but by 20% in relative terms (2 ÷ 10 × 100).