Percentage Change Calculator
Prices rise, salaries grow, traffic drops — percentage change is how we compare “before” and “after” fairly, regardless of scale. This calculator shows the percentage change, the absolute difference and the multiplier between any two values.
A positive result is an increase, negative is a decrease: going from 80 to 100 is +25%, while going back from 100 to 80 is −20%.
Enter valid values to see the results.
Formula
The change is always measured against the starting value, which is why the way up and the way down give different percentages. A 25% increase followed by a 25% decrease does not return to the start: 100 → 125 → 93.75.
What you need
- Starting value: the earlier or original number — last year’s price, the old salary, yesterday’s visitors.
- Final value: the later or new number, measured in the same units.
- The result sign tells the direction: positive = increase, negative = decrease.
Worked example
Practical tips
- To apply a percentage change directly, multiply by 1 ± the decimal: +8% means × 1.08, −12% means × 0.88.
- Reverse a change with division: if a price after +25% is $100, the original was 100 ÷ 1.25 = $80.
- Compare percentage points vs percent carefully: an interest rate moving from 3% to 4% rose by 1 percentage point but by 33%.
- For growth over several periods, use the Compound Interest Calculator — repeated percentage growth compounds.
Common changes and their multipliers
| Change | Multiplier | Reverse operation |
|---|---|---|
| +10% | × 1.10 | ÷ 1.10 (−9.09%) |
| +25% | × 1.25 | ÷ 1.25 (−20%) |
| +50% | × 1.50 | ÷ 1.50 (−33.3%) |
| +100% | × 2.00 | ÷ 2.00 (−50%) |
Common mistakes
- 1 Averaging percentage changes: +50% then −50% is not zero — it is −25% overall.
- 2 Using the final value as the base — the base is always the starting value.
- 3 Reporting a change from a tiny base as meaningful: “sales doubled” from 2 to 4 units is noise, not growth.
Frequently asked questions
How do I calculate percentage increase?
Subtract the start from the final, divide by the start, multiply by 100: from 50 to 65 is (15 ÷ 50) × 100 = +30%.
Why is the percent down different from the percent up?
Because the base changes. +25% from 80 reaches 100, but −25% from 100 falls to 75. The same absolute step is a different share of a different base.
How do I undo a percentage change?
Divide by the multiplier: after a 40% increase, divide by 1.40 to get the original. After a 40% decrease, divide by 0.60.
What is the difference between percent and percentage points?
Percentage points measure the arithmetic difference of two percentages (4% − 3% = 1 point); percent change measures it relative to the base (1 ÷ 3 = 33.3%).