Percentage Calculator
Three percentage calculators in one place: find a percent of a number, work out what percent one number is of another, and measure the percent change between two values. Every answer updates as you type.
What is X% of Y?
X is what percent of Y?
Percent change from X to Y
About this percentage calculator
One page for the three percentage questions that come up most often. Need a tip, a discount, or a slice of a total? Use X% of Y. Scoring a test or working out a share? Use X is what percent of Y. Comparing a before and after — a price rise, a weight loss, a stat that moved? Use percent change. Each calculator is independent, so you can keep all three filled in at once.
How to use it
- X% of Y multiplies the two together:
X ÷ 100 × Y. For 15% of 200 that is 30. - X is what percent of Y divides and scales:
X ÷ Y × 100. 30 out of 240 is 12.5%. - Percent change compares against the starting value:
(Y − X) ÷ X × 100, labelled as an increase or decrease. - Type into any field and the result recalculates instantly — there is no calculate button to press.
Is my input private?
Yes. Every calculation runs in your browser with JavaScript. Nothing you type is sent to a server, saved, or shared — close the tab and it is gone.
What happens if I divide by zero?
When the value you divide by is zero, the percentage is undefined, so the result shows a dash and a short note rather than a wrong number. Percent change from zero is undefined for the same reason — there is no baseline to compare against.
How are the results rounded?
Answers are shown to up to four decimal places and trimmed of trailing zeros, with thousands separators for large numbers. The full-precision value is used internally, so chaining results stays accurate.
What is the difference between percent change and percentage points?
This tool measures relative change. Going from 10% to 15% is a 50% increase here (5 is half of 10), whereas the gap of "5 percentage points" is an absolute difference. Use percent change for growth and decline; use percentage points when comparing two rates directly.