Percent Change Calculator
The percentage increase or decrease between two numbers.
Input sheet
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When a price, a salary, a stock, or a metric moves from one value to another, the raw difference rarely tells the whole story. Percent change expresses that move relative to where it started, so a $30 jump means very different things on a $40 item versus a $4,000 one.
How it works
(new − old) ÷ |old| × 100. Positive is an increase, negative a decrease.
The change is measured against the original (old) value, not the new one. That is why going up 50% and then down 50% does not return you to where you started — the second 50% is taken from a larger base.
This tool divides by the absolute value of the starting number, so it still returns a sensible percentage even when the original value is negative.
Percent change = (new − old) ÷ |old| × 100
Worked examples
A subscription price rising from $120 to $150. → +25.0% increase
(150 − 120) ÷ 120 = 30 ÷ 120 = 0.25, which is a 25% increase.
A stock falling from $80 to $60. → −25.0% decrease
(60 − 80) ÷ 80 = −20 ÷ 80 = −0.25, a 25% drop.
Tips & gotchas
- Order matters: percent change from A to B is not the negative of B to A. Going from 100 to 150 is +50%, but 150 back to 100 is only −33%.
- For percentage-point comparisons (e.g. an interest rate moving from 3% to 4%), say 'one percentage point,' not '1%.' That rate actually rose 33%.
- A drop can never exceed 100% — the most you can lose is the whole thing. An increase has no ceiling.
FAQ
What is the difference between percent change and percent difference?
Percent change has a clear before and after, measured against the starting value. Percent difference compares two values with no order, dividing by their average instead.
Why does a 50% gain not cancel a 50% loss?
Each percentage is taken from a different base. $100 up 50% is $150; $150 down 50% is $75. You end below where you began.
How do I reverse a percent change?
If something grew by a rate r, divide the new value by (1 + r) to recover the original. A value that is 25% higher is the new figure ÷ 1.25.
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