Percentage Calculator
Calculate percentages, percentage of a number, and percentage change.
How it works
Percentages come up constantly -- working out a discount, checking exam scores, comparing growth between two periods -- but the three common percentage problems each use a different formula, which is where most manual calculation mistakes happen. This calculator handles all three in one place.
"X% of Y" answers questions like "what is 20% of 150?" -- useful for tips, discounts, and commission. "X is what percent of Y" flips that around: if you scored 42 out of 60, what percentage is that? And "percentage change" tells you the percent increase or decrease between an original value and a new one -- the calculation behind revenue growth, price changes, or year-over-year comparisons.
Just select the calculation type, enter your two numbers, and get an instant, exact result -- no need to remember which formula applies to which situation.
Frequently asked questions
How do I calculate percentage increase?
Use the 'percentage change' mode: enter the original value as X and the new value as Y. A positive result is an increase, negative is a decrease.
What's the formula for 'X is what percent of Y'?
Divide X by Y and multiply by 100: (X / Y) × 100. For example, 42 out of 60 is (42/60) × 100 = 70%.
How do I find 20% of a number?
Use 'X% of Y' mode with X = 20 and Y = your number. The formula is (20/100) × Y.
Why is percentage change based on the original value, not the average?
Percentage change measures relative movement from a starting point, so it's always calculated against the original (X) value, not an average of the two -- this is the standard convention used in finance and statistics.