Percent change calculator
Enter an old value and a new value. You see how much it went up or down in percent. Use it for prices, pay, rent, investments or anything else.
(100 − 80) ÷ |80| × 100 = 25%. Difference: 20. Percent difference (no direction): 22.2222%.
Updated: October 2, 2026 · Sources and methodology
The percent change formula
percent change = (new − old) ÷ |old| × 100
A positive result is an increase. A negative result is a decrease. The old value is always the reference point. So the same two numbers give different answers in different directions.
Worked example: a rent increase
- Rent goes from $1,500 to $1,620. The change is 1,620 − 1,500 = $120.
- Divide by the old rent: 120 ÷ 1,500 = 0.08.
- Multiply by 100: the rent rose 8%.
Gains and losses aren't symmetric. A stock that falls from $50 to $35 lost 30%. Climbing from $35 back to $50 takes a 42.8571% gain. Stop on that gap for a second. The loss and the recovery are not the same size.
Percent change examples
| Example | Old | New | Change |
|---|---|---|---|
| Rent renewal | 1,500 | 1,620 | +8% |
| Gas price | 3.4 | 3.1 | -8.8235% |
| Hourly wage | 18 | 20.5 | +13.8889% |
| Stock price | 50 | 35 | -30% |
| Grocery bill | 120 | 138 | +15% |
| Stock recovery | 35 | 50 | +42.8571% |
Percent change vs. percent difference vs. percentage points
Percent change compares a new value with an old one, so direction matters.
Percent difference compares two values with no "before" and "after". Think of two stores' prices. It divides the gap by their average: |a − b| ÷ ((a + b) ÷ 2) × 100. The calculator shows both.
Percentage points describe the gap between two rates. Say a mortgage rate moves from 6% to 7%. It rose 1 percentage point. The rate itself rose 16.6667%. Both are true. Inflation is a percent change too. The Bureau of Labor Statistics publishes the 12-month percent change in the Consumer Price Index (bls.gov/cpi).
Frequently asked questions
How do you calculate percent increase?
Subtract the old value from the new value. Divide by the old value. Multiply by 100. From 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%.
How do you calculate percent decrease?
Use the same formula. The result is negative. From 100 to 80 is (80 − 100) ÷ 100 × 100 = −20%. That is a 20% decrease.
Why isn't a 50% drop undone by a 50% gain?
Each percent starts from a different point. $100 down 50% is $50. $50 up 50% is only $75. To get back to $100 from $50, you need a 100% gain.
Can percent change be more than 100%?
Yes, for increases. Going from 20 to 50 is a 150% increase. A decrease can't go below −100% unless the value turns negative.
What if the original value is zero?
Percent change from zero is undefined. You can't divide by zero. Report the plain difference instead.