Percentage Change Calculator
Find the percentage increase or decrease from an original value to a new one, with the exact amount of change shown alongside the percentage.
That is a increase of 20 (from 80 to 100).
Quick answer
Percentage change is the difference between two values divided by the original, times 100: ((new − old) / |old|) × 100. Going from 80 to 100 is ((100 − 80) / 80) × 100 = +25% (an increase); going from 100 to 80 is −20% (a decrease). This calculator labels the direction and shows the raw change.
Formula & method
The tool subtracts the original value from the new value to get the change, divides by the absolute value of the original, and multiplies by 100. A positive result is an increase, a negative result is a decrease. The change is undefined when the original value is 0 because it would divide by zero.
Examples
- Input
- from 80 to 100
- Result
- +25%
- Why
- (100 − 80) / 80 × 100 = 25% increase; change of +20.
- Input
- from 100 to 80
- Result
- −20%
- Why
- (80 − 100) / 100 × 100 = −20% decrease; change of −20.
- Input
- from 50 to 75
- Result
- +50%
- Why
- (75 − 50) / 50 × 100 = 50% increase.
When to use this tool
- Measuring growth or decline in price, revenue, weight, or scores.
- Comparing before-and-after figures in a report.
- Tracking how much a value rose or fell over time.
Common mistakes
- Dividing by the new value instead of the original — percentage change is always relative to the starting number.
- Assuming a +50% then −50% returns to the start: 100 → 150 → 75, not back to 100.
- Confusing percentage change with percentage points (e.g. 10% to 12% is a 2-point rise but a 20% increase).
Frequently asked questions
What is the percentage change formula?
((new value − old value) ÷ |old value|) × 100. A positive answer is an increase; a negative answer is a decrease.
What is the difference between increase and change?
Percentage increase is a positive percentage change; percentage decrease is a negative one. This tool shows the signed percentage and labels the direction.
Why can't I use 0 as the original value?
The formula divides by the original value, and dividing by zero is undefined, so a starting value of 0 has no percentage change.
Is percentage change the same as percentage difference?
No. Percentage change is relative to the original value. Percentage difference divides by the average of the two values and is always positive.
How do percentage points differ?
A move from 10% to 12% is a rise of 2 percentage points, but a 20% percentage increase relative to 10%.
Does it round the result?
It shows a tidy value with trailing zeros trimmed; the underlying calculation is exact.
Sources & references
External references open in a new tab. We are independent and not affiliated with these organizations.
- ✓ Free to use
- ✓ No sign-up required
- ✓ Runs entirely in your browser — nothing is uploaded.
- ✓ Formula and method shown above
Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.
Built and reviewed by HIFreeTools against the formula shown above and any authoritative references cited on this page. See our methodology and editorial standards.
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