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Percentage Calculator

Solve every everyday percent problem with the working shown: X% of Y, X is what percent of Y, percent change, percent difference, increase or decrease by a percent, and reverse percentages.

Question

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How it works

X% of Y = Y × X ÷ 100 · X as % of Y = X ÷ Y × 100 · X is Y% of W: W = X ÷ (Y ÷ 100) · % change = (Y − X) ÷ |X| × 100 · % difference = |X − Y| ÷ ((|X| + |Y|) ÷ 2) × 100 · Y changed by X% = Y × (1 ± X ÷ 100) · original = Y ÷ (1 ± X ÷ 100)

A percent is a fraction with 100 on the bottom, so every percent question is a multiply or a divide. Finding X% of Y multiplies Y by the decimal form of the percent. Asking what percent X is of Y divides the part by the whole and multiplies by 100, and the reverse question (X is Y% of what?) divides the part by the percent’s decimal. Increasing or decreasing by X% multiplies by (1 + X ÷ 100) or (1 − X ÷ 100), and undoing a change divides by that same multiplier — which is why removing a 20% markup means dividing by 1.2, not taking 20% off. Percent change measures growth from a starting value, so it divides the difference by the start; percent difference compares two values with neither one as the reference, so it divides by their average. Every answer comes with the worked steps, and you can round results to a fixed number of decimals under More options.

Worked example

What is 25% of 200? Convert 25% to 0.25 and multiply: 200 × 0.25 = 50. Flipped around, 50 ÷ 200 × 100 = 25%, and 50 is 25% of 50 ÷ 0.25 = 200. A price that goes from 40 to 50 has changed by (50 − 40) ÷ 40 × 100 = +25%, while the percent difference between 40 and 50 is 10 ÷ 45 × 100 = 22.22%. If a price of 120 already includes a 20% markup, the original was 120 ÷ 1.2 = 100.

Frequently asked questions

What is the difference between percent change and percent difference?

Percent change has a direction: it measures how much a value grew or shrank from a starting point, so it divides by the old value (40 to 50 is +25%, 50 to 40 is −20%). Percent difference treats both values equally and divides by their average, so 40 and 50 are 22.22% apart whichever way you compare them.

How do I find the original number before a percent increase?

Divide by the growth multiplier. If 138 is 15% more than the original, the original is 138 ÷ 1.15 = 120. Subtracting 15% of 138 would give 117.30, which is wrong because the 15% was taken of the smaller, original number.

What is the difference between percent and percentage points?

Percentage points measure the plain gap between two percentages, while percent change measures it relative to the starting one. A rate that moves from 4% to 5% rose by 1 percentage point but by 25% in percent terms.

How do I convert a percent to a decimal?

Divide by 100, which moves the decimal point two places left: 25% = 0.25, 7.5% = 0.075, 150% = 1.5. To go the other way, multiply by 100.

Can a percentage be more than 100%?

Yes. 250% of 40 is 100 — percentages over 100 simply mean more than the whole. They show up constantly in growth figures and markups. A decrease, however, can’t go past 100% without the value turning negative.