How to use this percentage change calculator
- Old value, enter the starting number (the value before the change).
- New value, enter the number you ended up with (the value after the change).
- Read the percentage change, the direction (increase or decrease) and theabsolute difference, they update instantly as you type.
Nothing is submitted or stored: the numbers never leave your device, so you can run figures privately.
How percentage change is calculated
Percentage change measures how much a number has moved from a starting point. The formula ispercent change = (new value - old value) / absolute(old value) × 100. You subtract the old value from the new value to get the difference, divide that by the absolute value of the old value, then multiply by 100 to turn it into a percentage. A positive result means an increase, and anegative result means a decrease. If the old value is 0 there is nothing to divide by, so the percentage cannot be defined.
Worked example
Suppose a price rose from 50 to 75. The difference is 75 - 50 = 25. Dividing by the absolute old value gives 25 / 50 = 0.5, and multiplying by 100 gives a 50% increase. If the price instead fell from 75 to 50, the difference is -25, so the change is -25 / 75 × 100 ≈ 33.33% decrease. Notice that the same gap produces a different percentage depending on which number you start from, because the old value is the baseline.
Where percentage change is useful
Percentage change shows up everywhere: comparing this month's revenue to last month's, tracking a price rise or a sale discount, measuring weight or grade changes over time, or reporting growth in followers, views and traffic. Because it expresses movement relative to the starting value, it lets you compare changes fairly even when the raw numbers are very different in size.
Frequently asked questions
How do you calculate percentage change?
Subtract the old value from the new value, divide by the absolute value of the old value, then multiply by 100. Going from 50 to 75 is (75 - 50) / 50 × 100 = 50% increase.
What is the difference between percent increase and percent decrease?
A positive percentage change means the new value is higher than the old value (an increase). A negative percentage change means the new value is lower (a decrease).
Why does the percentage show a dash?
If the old value is 0, the percentage cannot be worked out because you cannot divide by zero. The tool still shows the absolute difference.
Is percentage change the same as percentage difference?
No. Percentage change has a clear before and after, so the order matters. Percentage difference compares two values without a baseline, dividing by their average instead.
Is my data uploaded?
No, everything is calculated on your device and nothing is sent anywhere.