Percentage Change Calculator
Calculate the percentage increase or decrease between two values, find a new value after a known percentage change, or reverse-calculate the original value — all instantly in your browser.
All calculations happen in your browser. No data is sent anywhere.
Percentage Change
Enter the original and new values to find the percentage increase or decrease between them.
Results
| Percentage Change | — |
|---|---|
| Direction | — |
| Absolute Difference | — |
Find New Value
Know the original value and the percentage change? Calculate what the new value will be.
Results
| New Value | — |
|---|---|
| Absolute Difference | — |
| Direction | — |
Find Original Value
Know the new value and the percentage change that was applied? Reverse-calculate the original value.
Results
| Original Value | — |
|---|---|
| Absolute Difference | — |
Understanding Percentage Change
The percentage change formula
Percentage change measures how much a quantity has shifted relative to its starting point. The formula is:
% Change = ((New − Old) / |Old|) × 100
Using the absolute value of the old number handles cases where the original value is negative. A positive result is an increase; a negative result is a decrease.
- Example: Price rises from $40 to $50 → ((50 − 40) / 40) × 100 = +25%.
- Example: Revenue falls from 1,000 to 800 → ((800 − 1,000) / 1,000) × 100 = −20%.
- The old value cannot be zero — division by zero is undefined.
% Change vs. % Difference
These two are often confused but mean very different things:
- Percentage change — has a clear "before" (old) and "after" (new). Direction matters. Formula uses the old value as the denominator.
- Percentage difference — no implied order. Uses the average of both values as the denominator: |A − B| / ((A + B) / 2) × 100.
Use percentage change for time-series comparisons (last year vs. this year). Use percentage difference when comparing two items with no natural starting point (e.g., comparing two cities' populations).
Percentage change in finance
Finance relies heavily on percentage change to communicate performance without requiring the reader to know absolute figures:
- Stock returns — if a share moves from $25 to $31, the return is +24%.
- Revenue growth — year-over-year growth rates allow comparison across companies of different sizes.
- Inflation — CPI percentage change shows how prices have shifted relative to a base period.
- Compound growth — applying percentage change repeatedly yields compounding. Use the CAGR calculator for multi-year periods.
Common mistakes to avoid
Even simple percentage change calculations trip people up. Watch out for these pitfalls:
- Confusing % change with percentage points — if an interest rate moves from 2% to 3%, that is 1 percentage point but a 50% change in the rate.
- Asymmetry of increases and decreases — a 50% decrease followed by a 50% increase does not return to the original value. (100 → 50 → 75, not 100.)
- Negative starting values — when the old value is negative, the sign of the percentage change can be counter-intuitive. Always check the absolute difference alongside the percentage.
- Rounding early — round only the final displayed result, not intermediate values.
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Calculate ROI →FAQ
How do you calculate percentage change?
Use the formula: % Change = ((New Value − Old Value) / |Old Value|) × 100. A positive result means an increase; a negative result means a decrease. For example, if a price rises from $80 to $100: ((100 − 80) / 80) × 100 = +25%. Enter your values in the "Percentage Change" tab above to calculate instantly.
What is the difference between percentage change and percentage difference?
Percentage change has a clear before (old) and after (new) — it measures directional movement relative to the old value. Percentage difference has no implied order; it uses the average of both values as the denominator: |A − B| / ((A + B) / 2) × 100. Use percentage change for before-and-after comparisons, and percentage difference when neither value is the clear starting point.
What does a negative percentage change mean?
A negative percentage change means the value decreased. For example, if sales fall from 500 to 400, the percentage change is ((400 − 500) / 500) × 100 = −20%, meaning a 20% decrease. The sign tells you the direction: positive = increase, negative = decrease.
How do you find the original value from a percentage change?
Rearrange the percentage change formula: Original = New Value / (1 + % Change / 100). For example, if a value is now 120 after a 20% increase, the original was 120 / 1.20 = 100. Use the "Find Original Value" tab above to reverse-calculate automatically.
What is the difference between percentage change and percentage points?
Percentage points (pp) measure the arithmetic difference between two percentages. If an interest rate rises from 3% to 5%, it increased by 2 percentage points. However, the percentage change in the rate itself is ((5 − 3) / 3) × 100 ≈ 66.7%. These two measures can differ dramatically — always specify which one you mean to avoid misinterpretation.