Percentage Increase Calculator
Enter two numbers to get the percentage change between them. The result updates as you type and shows the formula worked out with your own figures, so you can check the arithmetic or copy the method.
The formula
percent change = (ending − starting) ÷ |starting| × 100
In words: subtract the starting value from the ending value, divide by the starting value, and multiply by 100. A positive result is an increase; a negative result is a decrease.
Going from 120 to 150: the difference is 30, divided by 120 gives 0.25, times 100 is a 25% increase.
The mistake almost everyone makes
A 50% increase followed by a 50% decrease does not bring you back to where you started.
Start at 100. Add 50% and you have 150. Now take 50% off 150 and you have 75 — not 100. The percentages are calculated against different bases: the increase was against 100, the decrease against 150.
This is why the calculator shows a separate "change needed to go back" figure. If a number rises by 25%, it has to fall by 20% to return to the original. If it rises by 100%, it has to fall by 50%. The larger the increase, the more asymmetric the pair becomes.
This matters more than it sounds. An investment that drops 50% needs a 100% gain to recover. A price cut of 30% needs a 43% rise to undo. Any time someone quotes a percentage recovery after a percentage fall, check which base they used.
Percentage change vs percentage point change
These get confused constantly, and the difference can be a factor of ten.
If an interest rate moves from 2% to 3%, that is a rise of one percentage point — but a 50% increase in the rate itself. Both statements are correct and they describe the same event. When the underlying quantity is itself a percentage, always say which one you mean.
Use "percentage points" when comparing two percentages directly. Use "percent change" when describing how much a quantity grew relative to its own starting size.
Negative starting values
When the starting value is negative, the sign convention gets ambiguous, and different sources handle it differently. This calculator divides by the absolute value of the starting number, so a move from −50 to −25 reports as a 50% increase — the value went up, and the result says so.
Some references divide by the signed value instead, which would report the same move as a 50% decrease. Neither is wrong, but they are not interchangeable, so if you are reconciling against another tool, check which convention it uses.
Percentage change from zero
If the starting value is zero, percentage change is mathematically undefined — you would be dividing by zero. There is no meaningful percentage answer to "we went from 0 sales to 40 sales." Report the absolute change instead, or use a different baseline.
Quick reference
| From → To | Change | To get back |
|---|---|---|
| 100 → 110 | +10% | −9.09% |
| 100 → 125 | +25% | −20% |
| 100 → 150 | +50% | −33.33% |
| 100 → 200 | +100% | −50% |
| 100 → 90 | −10% | +11.11% |
| 100 → 75 | −25% | +33.33% |
| 100 → 50 | −50% | +100% |
Frequently asked questions
How do I calculate percentage increase?
Subtract the starting value from the ending value, divide the result by the starting value, and multiply by 100. Going from 120 to 150: (150 − 120) ÷ 120 × 100 = 25%.
Why does a 50% increase followed by a 50% decrease not return me to the start?
Because the two percentages are applied to different bases. The increase is calculated on the original number, the decrease on the larger number that resulted. Start at 100, add 50% to reach 150, then remove 50% of 150 and you land at 75.
What is the difference between percent change and percentage points?
A move from 2% to 3% is a one percentage point rise, but a 50% increase in the rate itself. Use percentage points when directly comparing two percentages, and percent change when describing growth relative to a starting size.
Can I calculate percentage change from zero?
No — it is mathematically undefined, because the formula would divide by zero. Report the absolute change instead, or pick a different baseline period.
How does this handle negative starting values?
It divides by the absolute value of the starting number, so a move from −50 to −25 reports as a 50% increase. Some other tools divide by the signed value and would call the same move a decrease, so check the convention if you are comparing results.