Percentage Change Calculator
Enter an old value and a new value to see the percent change, whether it is an increase or a decrease, the absolute difference, and the multiplier, live as you type.
Everything is calculated in your browser. The numbers you type are never uploaded.
How to calculate percentage change online
Enter the old value
Type your starting or original number into the old value field.
Enter the new value
Type the number you are comparing it to into the new value field, and the percent change appears instantly.
Read the change
See the signed percent change, whether it is an increase or a decrease, the absolute difference, and the multiplier.
Apply a change in reverse
Switch to apply mode to grow or shrink a starting value by a percentage and read the resulting value.
Why use this tool
Signed percent change
The result carries a plus or minus sign and states increase or decrease, so the direction of the change is never ambiguous.
Difference and multiplier too
Alongside the percentage you get the absolute difference between the two values and the multiplier, which is the new value divided by the old.
Apply a change in reverse
Switch to apply mode to grow or shrink a starting value by a percentage you choose and read the resulting value straight away.
Handles zero and negative values
When the old value is zero the tool explains that the percent change is undefined instead of showing a broken figure, and negative values are measured correctly.
Live results as you type
Every field recalculates the moment a number changes. There is no button to press and nothing to submit.
Runs entirely in your browser
Everything happens on your device; the numbers you type are never uploaded.
About this tool
Percentage change measures how much a value has grown or shrunk relative to where it started. The formula is the new value minus the old value, divided by the size of the old value, times one hundred. A price moving from 80 to 92 is a plus 15 percent increase, while the reverse move from 92 back to 80 is a minus 13.04 percent decrease. The two are not the same, because change is always measured against the starting value, and swapping them is one of the most common mistakes people make with percentages.
This calculator reports three things at once: the signed percent change, the absolute difference between the two values, and the multiplier, which is simply the new value divided by the old. The multiplier is handy for spreadsheets and quick mental checks, since a plus 15 percent change is the same as multiplying by 1.15. Switch to apply mode to work the other way and grow or shrink a starting value by a percentage you choose. When the old value is zero the percent change is undefined, so the tool says so plainly rather than showing a broken figure, and negative values are handled by measuring the change against the size of the starting number.
Every number is calculated on the page as you type, and nothing is uploaded or stored. For related jobs, the percentage calculator finds a percent of a number, the markup calculator works out selling prices from cost, and the discount calculator handles sale prices.
Frequently asked questions
- How is percentage change calculated?
- Subtract the old value from the new value, divide by the size of the old value, and multiply by 100. Going from 80 to 92 is a plus 15 percent increase; going from 92 back to 80 is a minus 13.04 percent decrease, because the change is always measured against where you started.
- What is the difference between percent change, absolute difference, and multiplier?
- The percent change is the relative change as a percentage. The absolute difference is the plain new value minus the old value. The multiplier is the new value divided by the old, so a plus 15 percent change equals a multiplier of 1.15.
- Why does it say the change is undefined?
- Percentage change divides by the old value, and dividing by zero has no answer. When the old value is zero the tool reports the change as undefined and still shows the absolute difference, which is defined.
- Can I apply a percentage change to a number?
- Yes. Switch to apply mode, enter a starting value and a percent change such as plus 15 or minus 20, and the tool shows the resulting value along with the difference and the multiplier.
- Does it handle negative numbers?
- Yes. Negative old and new values are accepted, and the change is measured against the size of the starting value so the sign always matches the direction the value actually moved.
- Is my data uploaded anywhere?
- No. Everything runs in your browser; nothing is sent to a server. The numbers you type are never uploaded, stored, or logged.
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