How to Use
Select the calculation type: "X% of Y" for finding a portion, "X is what % of Y" for finding the rate, or "Percent change" for comparing two values.
Enter the known values in the input fields for the selected mode.
Click Calculate to compute the result.
Read the result and any explanatory breakdown shown below the inputs.
What Is a Percentage Calculator?
A percentage calculator solves the three fundamental percentage problems: (1) What is X% of Y - for example, 20% of 350 equals 70; (2) X is what percent of Y - for example, 70 is 20% of 350; (3) Percent change from X to Y - for example, a change from 350 to 420 is a 20% increase. Real-world uses include calculating sale discounts, tip amounts, tax, grade percentages, and investment returns. One critical distinction to understand: a percentage point and a percentage are different things. If a loan interest rate rises from 10% to 12%, that is a 2 percentage point increase but a 20% relative increase. These two framings are routinely confused in media, advertising, and political reporting.
Why Does Accurate Percentage Calculation Matter?
Percentage confusion is routinely exploited in sales and advertising. "50% off, then an additional 20% off" is not 70% off - it is 60% off (you pay 50% of the original, then 80% of that, which equals 40% of the original price). Stacking discounts never adds up the way it sounds. Politicians and marketers frequently swap percentage points and percentages to exaggerate or minimize changes depending on which framing is more favorable. Calculating percentages accurately lets you verify claimed discounts, tax amounts, and rate changes independently.
Worked example: reversing a percentage change
A common mistake is trying to undo a percentage increase by subtracting the same percentage. Suppose an item that cost 80 rose by 25% to 100. Taking 25% off 100 gives 75, not 80 - because the two percentages are applied to different base numbers. To reverse an increase, divide by 1 plus the rate: 100 / 1.25 = 80. To find the pre-discount price of something now selling for 90 after 25% off, divide by 1 minus the rate: 90 / 0.75 = 120. The takeaway: an increase and a decrease of the same percentage never cancel out, so always divide to work backwards rather than adding the percentage back.