Pick the calculation you need from the dropdown, enter the two numbers, and the result updates as you type.
For worked examples of each calculation type, see the percentage calculator step-by-step guide.
Percentage Calculator
Work out a percentage of a number, the reverse (what percent one number is of another), or a percent change, right in the browser, with the result updating as you type.
Key features
- Pick the calculation you need from the dropdown and enter the two numbers; the result updates as you type - no button to click.
- Switch calculations at any time; the two number fields carry over so you can compare results without re-typing them.
When to use it
Use it for a discount, a tax add-on, a grade, or comparing two values as a percent change.
Privacy
The two numbers you enter stay in the browser - the result is computed on this device, with no upload and no account. The figures are gone when you leave the page and are never sent to an analytics or tracking service.
Accuracy
The result is a general estimate, not financial or professional advice.
How the three calculations work, with a worked example
Percentage Calculator opens with the two fields already filled in - X set to 20, Y set to 80 - so a real result is visible the moment the page loads, before you type anything. The first mode, what is X% of Y, multiplies: 20% of 80 works out to 16. The second mode, X is what percent of Y, divides the other way: 20 is 25% of 80. The third mode, percent change from X to Y, measures the relative move between the two numbers: going from 20 to 80 is a change of plus 300%, while going the other way, from 80 to 20, is a change of minus 75% - the sign shows whether the value rose or fell. Switching modes relabels the two fields to match what you are solving for: "Percent (%)" and "Of value" for the first mode, "Value" and "Out of (total)" for the second, "From value" and "To value" for the third, so it stays clear which number belongs where without needing to remember the order.
What happens with a zero starting value
Two of the three modes divide by one of your numbers, and dividing by zero has no real answer, so Percentage Calculator checks for that case before it calculates. Set Y to zero while using X is what percent of Y and the result area shows "Enter a non-zero total." instead of a broken calculation. Set X to zero while using percent change from X to Y and it shows "Enter a non-zero starting value." instead of dividing by it. The first mode, what is X% of Y, never divides by either field, so a zero there calculates normally - 0% of 80 is 0, and 20% of 0 is also 0.
Frequently Asked Questions
What does Percentage Calculator do?
Work out a percentage of a number, the reverse (what percent one number is of another), or a percent change.
When should I reach for percentage calculator?
Use it for a discount, a tax add-on, a grade, or comparing two values as a percent change.
What complementary tools work well alongside percentage calculator?
Switch calculations at any time; the two number fields carry over so you can compare results.
Do the field labels change depending on which calculation I pick?
Yes. The two input labels switch to match the selected mode: "Percent (%)" and "Of value" for what is X% of Y, "Value" and "Out of (total)" for X is what percent of Y, and "From value" and "To value" for percent change from X to Y.
What happens if I leave a field blank or type something that is not a number?
It is read as 0, not rejected. That is safe for the first mode (what is X% of Y), but the second and third modes catch a zero denominator first and show a message asking for a non-zero value instead of calculating.
How many decimal places does the result show?
Up to 4, formatted with your browser's own thousands separator - fewer digits when the result is a whole number, so the display never shows more precision than the calculation actually has. For example, 1 is what percent of 3 shows 33.3333%, not the full repeating decimal.