Enter the value before a change and the value after it. The calculator shows the amount added, the percentage change, and the equation used. The other two modes work backwards: one finds the new value after a known increase, and one recovers the original value.
Created and checked by Badar Ashfaq. The edge cases used to check this calculator are recorded in the public testing register.
Choose the calculation that matches your numbers
| What you know | What you need | Mode to use |
|---|---|---|
| Original and new values | Percentage increase | Find % Increase |
| Original value and increase rate | New value | Find New Value |
| New value and increase rate | Original value | Find Original Value |
Percentage increase formula
Percentage increase = ((new value − original value) ÷ original value) × 100
An increase from 600 to 680 is 80. Divide 80 by the starting value of 600, then multiply by 100. The result is 13.3333%, normally shown as 13.33%. The starting value belongs in the denominator; dividing by 680 answers a different question.
Four checked examples
| Change | Amount added | Percentage increase |
|---|---|---|
| 80 to 100 | 20 | 25% |
| 130 to 156 | 26 | 20% |
| 600 to 680 | 80 | 13.3333% |
| 65,000 to 75,000 | 10,000 | 15.3846% |
Finding a new value—or reversing an increase
To apply an increase, use new value = original value × (1 + rate ÷ 100). A value of 200 increased by 25% becomes 200 × 1.25 = 250.
To work backwards, use original value = new value ÷ (1 + rate ÷ 100). If 125 is the result after a 25% increase, 125 ÷ 1.25 gives an original value of 100. Simply taking 25% off 125 would use the wrong base.
Percentage points are not percentage increase
If a rate moves from 3% to 4%, it has risen by one percentage point. Relative to the old rate, however, it has increased by 33.33%. Say which measure you mean when comparing interest rates, survey results, tax rates, or conversion rates.
Zero, decreases, negative values, and rounding
- A percentage change from zero is undefined because the formula would divide by zero. The calculator flags that case instead of inventing an answer.
- When the new value is smaller, the result is a decrease. Moving from 100 to 80 is a 20% decrease.
- A negative starting value can be mathematically valid, but its real-world meaning depends on the situation. The result explains the method used.
- The calculation keeps browser precision and rounds only the displayed answer. Contracts and regulated reports may require a specific rounding rule.
Reviewed 19 September 2026. Checks include 100→125, 600→680, decimal inputs, a zero starting value, a decrease, and both reverse modes. If you can reproduce a mismatch, send the inputs, selected mode, and displayed result through the Contact page.