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Percentage Calculator

Three percentage calculators in one: what is X% of Y, X is what % of Y, and percentage change.

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What is%% of

What is 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.

How to use

  1. 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.
  2. Enter the known values in the input fields for the selected mode.
  3. Click Calculate to compute the result.
  4. Read the result and any explanatory breakdown shown below the inputs.

Why it matters

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.

Pro tip

Mental math shortcuts for everyday percentages: 10% means move the decimal point one place left. 5% is half of 10%. 15% is 10% plus 5%. 20% is double the 10% value. 25% means divide by 4. These five rules cover most tip, discount, and tax estimates without any calculator — fast enough to verify a restaurant bill or a store discount in seconds.

Frequently Asked Questions

Multiply the number by X and divide by 100. For example, 15% of 200 = 200 × 15 ÷ 100 = 30.
Divide the first number by the second, then multiply by 100. For example, 30 is what percent of 200? 30 ÷ 200 × 100 = 15%.
Subtract the old value from the new value, divide by the old value, and multiply by 100. Formula: ((new - old) / old) × 100.
A positive result means the value increased (percentage increase). A negative result means the value decreased (percentage decrease).
Yes — all three calculators accept decimal inputs like 12.5 or 0.75.