Free percentage change calculator
Calculate the percentage increase or decrease between two values — enter the original and new values to see the % change, updated live, as you type.
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Formula: (new − old) ÷ old × 100. Positive = increase.
Results are estimates. Consult a professional.
How the percentage change calculator works
Percentage change measures how much a quantity has grown or shrunk relative to its starting value. A positive result is an increase; a negative result is a decrease. The formula always uses the original (old) value as the reference so that the direction is unambiguous.
Worked example: price rises from $80 to $100
A product's price increases from $80 to $100. How much did the price change in percentage terms?
Common percentage change scenarios
The table below shows quick examples across business, science, and everyday contexts.
| Scenario | Old value | New value | % Change |
|---|---|---|---|
| Salary raise | $50,000 | $55,000 | +10% |
| Product discount | $120 | $90 | −25% |
| Population growth | 1,000,000 | 1,080,000 | +8% |
| Temperature drop | 20 °C | 15 °C | −25% |
| Battery capacity | 3,000 mAh | 4,500 mAh | +50% |
| Stock price fall | $250 | $200 | −20% |
| Test score improvement | 65 | 78 | +20% |
Source: illustrative examples based on standard percentage change formula
Tips for working with percentage changes
Percentage changes are among the most misused statistics. These tips help you apply and interpret them correctly.
- Always identify "old" and "new" clearly — the base value goes in the denominator; swapping them produces a different (and wrong) percentage.
- Increases and decreases are not symmetric — a 50% rise followed by a 50% fall returns only 75% of the original value, not 100%.
- Avoid "percent change" for negative bases — when the old value is zero or negative (e.g. a loss turning to a profit), percentage change is misleading; report absolute change instead.
- Compound vs simple change — applying a 10% increase three years in a row gives 1.10³ − 1 = 33.1% total, not 30%; use compound growth for multi-period analysis.
- Check whether the context needs percent difference — percent difference (used when neither value is the "reference") divides by the average of the two values, not the old one.
Accuracy and limitations
This calculator is undefined when the old value is zero — you cannot express a change relative to a zero baseline as a percentage. Results are computed in IEEE 754 double precision; for inputs within the normal range of everyday values the output is accurate to at least 12 significant figures. The calculator computes a single-step percentage change. For multi-period or compound growth analysis, see the compound annual growth rate (CAGR) calculator.
Key terms
About this calculator
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