Math and everyday tool
Make percentage questions
easy to answer.
Calculate a percent, compare two values, or check a percentage change. Each result updates in this browser, with the formula kept visible so the number is easier to double-check.
What is p% of x?
Find a percentage of a number.
Enter a percent and a number.
x is what percent of y?
Compare a part with a whole.
Enter a part and a non-zero whole.
x is p% of what?
Work backward from a part and its percentage.
Enter a part and a non-zero percent.
What is the percentage change?
Compare an old value with a new value.
Enter an old value and a new value.
Frequently asked questions
Are my numbers uploaded?
No. The calculations run in this browser page. The tool does not send or store the numbers you enter. The page still loads the shared site assets and advertising script.
How is percentage change calculated?
Percentage change is (new value − old value) ÷ old value × 100. A positive result means the new value is higher; a negative result means it is lower.
Can I use negative or decimal values?
Yes. Valid finite numbers, including negative and decimal values, are accepted. A zero old value cannot be used as a percentage-change baseline.
Which percentage calculation should I use?
Use “p% of x” for a portion, “x is what percent of y” for a ratio, and percentage change to compare an old value with a new value.
Worked example
20% of 80 is 16. Increasing 80 to 100 is a 25% increase, while decreasing 100 to 80 is a 20% decrease: the starting value is different.
Limits to know
Percentage change from zero is undefined. A percentage-point difference is not the same as percentage change: 10% to 15% is 5 points and a 50% relative increase.