Percentage Calculator
Calculate percentages, and percentage change.
🔒 Runs entirely in your browser — nothing is uploaded.
What is X% of Y?
X is what percent of Y?
Percentage change from X to Y
How Percentage Calculator works
What formulas power the percentage calculator?
It runs three separate, independent calculations. X% of Y multiplies (X / 100) by Y; X is what percent of Y divides X by Y and multiplies by 100; and the percentage-change box computes ((Y - X) / X) * 100 to show how much a value moved from a starting point to an ending point. Every result is rounded to two decimal places as you type.
When would I reach for each of the three calculators?
Use the first box for things like figuring out a tip or a discount amount on a known price. The second is for turning a raw score into a percentage, such as 25 correct answers out of 200 questions. The third is built for tracking growth or decline, like comparing a test score, a bill, or a stock price between two points in time.
What happens if I enter zero as the starting value?
The "what percent of" and "percentage change" boxes both guard against dividing by zero — if the base number is 0, they simply return 0 instead of throwing an error or showing Infinity. It's worth noting the percentage-change formula is not symmetric: going from 50 to 75 is a +50% change, but going back from 75 to 50 is a -33.33% change, not -50%, because each calculation divides by its own starting value.