Percentage Change Calculator
Calculate percentage increase or decrease between two values. Also computes percentage difference and what value X% of a number is.
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How to use this calculator
Subtract old from new, divide by the absolute old value, multiply by 100.
- 1
Enter the original (old) value.
- 2
Enter the new value.
- 3
The calculator shows the percentage increase or decrease.
- 4
Percentage difference is symmetric — it compares two values without a reference direction.
Frequently asked questions
Why does the original value come first?
Percentage change is measured against the starting point: (new − old) ÷ |old| × 100. Swapping the two numbers changes the answer. Going from 100 to 150 is a 50% increase, while going from 150 back to 100 is a 33.3333% decrease. The Multiplier row (1.5x and 0.6667x) shows the same asymmetry.
What happens when the original value is 0?
The calculator returns “Original value cannot be 0”. Growth from zero is undefined as a percentage because the division is by zero. If you only want to describe the gap, use the absolute change instead.
How are negative values handled?
The denominator uses the absolute value of the old number, so the sign of the answer tracks the direction of movement. From -20 to -10 the value rose by 10, and the tool reports a 50% increase. From -5 to 5 it reports a 200% increase and a multiplier of -1x. Percentages across a sign change are hard to interpret, so check that this convention suits your purpose.
What is “Percentage Difference” and how is it different from change?
It compares two values without treating either as the starting point: the absolute difference divided by the average of the two magnitudes. For 100 and 150 it is 40% in either order, whereas the change is 50% one way and 33.3333% the other. Use it when neither value is the baseline.
Why does a 50% drop need a 100% gain to recover?
Because the base shrinks. Going from 100 to 50 is a 50% decrease; going from 50 back to 100 is a 100% increase. Equal-sized percentages in opposite directions do not cancel out.
What does 0% look like in the output?
If the two numbers are equal, the label still reads “Percentage Increase” with a value of 0%, and the multiplier is 1x. There is no separate “no change” label.
Is a percentage change the same as percentage points?
No. If a rate moves from 4% to 5%, the change is 1 percentage point, but the percentage change is 25%. Enter 4 and 5 and the tool reports the 25%, not the point difference, which is the Absolute Change row (1).
How is the output rounded?
Values are rounded to 4 decimal places with trailing zeros removed, so 33.3333% is a truncated repeating decimal. The tool does not round to whole percentages and does not apply any currency formatting.
Percentage change calculator — increase, decrease and difference
The formula and what the outputs mean
Percentage change is (new − old) ÷ |old| × 100. A positive result is an increase and a negative one a decrease; the tool reports the size and labels the direction. Below that it lists the absolute change, a symmetric percentage difference that uses the mean of the two values, and a multiplier (new ÷ old). A multiplier of 1.25x is exactly a 25% increase, and 0.75x is a 25% decrease.
Worked examples
These were all produced by running the calculator.
| Old → New | Change | Absolute change | Percentage difference | Multiplier |
|---|---|---|---|---|
| 80 → 100 | +25% | 20 | 22.2222% | 1.25x |
| 100 → 75 | −25% | 25 | 28.5714% | 0.75x |
| 100 → 150 | +50% | 50 | 40% | 1.5x |
| 150 → 100 | −33.3333% | 50 | 40% | 0.6667x |
| 50 → 0 | −100% | 50 | 200% | 0x |
| -20 → -10 | +50% | 10 | 66.6667% | 0.5x |
Asymmetry: why the direction matters
The pair 100 and 150 shows the key trap. Up from 100 is +50%, down from 150 is −33.3333%, yet the percentage difference is 40% both ways. Choosing which number is the baseline is part of the question you are asking. A price that falls from 100 to 50 has lost 50%, and it must then rise 100% to return. Report the base alongside the percentage so readers do not have to guess.
Typical uses
Comparing a monthly figure with the previous month, checking how much a salary changed (1,200 to 1,500 is a 25% increase with a 300 absolute change), or measuring a drop in a test score all use the same formula. When the original is the correct baseline, use the Change row. When you are comparing two measurements that are equally valid, such as two labs’ readings of the same sample, the percentage difference is the better summary.
Where the calculation breaks down
A zero original is rejected because the percentage would be infinite. Changes that cross zero, such as −5 to 5, give a 200% increase by this convention, which can be misleading for things like profit and loss. For rates and shares, remember to separate percentage points from percent: a move from 4 to 5 is one point but a 25% relative increase. Also keep the unit of both numbers identical before comparing them.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →