Percentage calculator
Four separate calculations on one page. Pick a mode, enter two numbers, and read the result. Nothing is sent to a server.
The four formulas
X percent of Y is Y times X divided by 100. X is what percent of Y is X divided by Y, times 100. X is Y percent of what number is X divided by Y percent. Percentage change from X to Y is Y minus X, divided by X, times 100. A positive change is an increase. A negative change is a decrease. Zero is no change.
Results are rounded to two decimal places. A whole number is shown without trailing zeros, so 30 stays 30, while a repeating value such as the drop from 75 to 50 is shown as -33.33. If a mode would divide by zero, the page says so. It does not show a blank or a broken number.
Questions
How is X percent of Y calculated?
The first mode multiplies Y by X divided by 100. So 20 percent of 150 is 150 times 0.20, which is 30. A percent can be larger than 100, and it can be a decimal or negative. The result is rounded to two decimal places, and trailing zeros are dropped when the value is whole.
How do you find what percent X is of Y?
Divide X by Y, then multiply by 100. So 30 compared with 150 is 0.20, which is 20 percent. If Y is zero, there is no percentage to report, and the page says so in plain words. Both values are typed on this page and are not sent anywhere.
What does percentage change mean?
Subtract the starting number from the later number, divide by the starting number, then multiply by 100. From 50 to 75 is a 50 percent increase. From 75 to 50 is a 33.33 percent decrease. If the start is zero, the page will not divide by zero. The label says increase, decrease, or no change.
Which of the four modes should I use?
Use X percent of Y when you know a rate and a whole. Use X is what percent of Y when you know two amounts and want the rate. Use X is Y percent of what when you know a part and a rate and want the whole. Use percentage change for the rise or fall between two numbers.