Percentage Calculator

Calculate percentages six ways — with step-by-step workings and a visual result

%
X% of Y
What is 20% of 150?
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X is what % of Y?
30 is what % of 150?
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% Change
From 80 to 100?
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% Increase
100 increased by 20%?
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% Decrease
100 decreased by 20%?
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Reverse %
30 is 20% of what?
What is X% of Y?

// Calculation History

Your calculations will appear here

// Percentage Formulas at a Glance

X% of Y
Y × X ÷ 100
X is ?% of Y
(X ÷ Y) × 100
% Change
((New−Old) ÷ Old) × 100
Y increased by X%
Y × (1 + X÷100)
Y decreased by X%
Y × (1 − X÷100)
X is Y% of ?
X ÷ (Y ÷ 100)

How to Calculate Percentages

A percentage is a way of expressing a number as a fraction of 100. The word "percent" comes from the Latin "per centum" — meaning "by the hundred". Percentages are used everywhere — discounts, tax, interest rates, statistics, grades, and more.

All Six Percentage Formulas

Common Percentage Mistakes

Mistake 1: "Adding percentages" — a 50% increase followed by a 50% decrease does NOT return to the original. 100 × 1.5 = 150, then 150 × 0.5 = 75. You end up 25% lower.

Mistake 2: Percentage of vs percentage change — "30 is 20% more than 25" is different from "30 is 20% of 150".

Mistake 3: Reverse percentage — if a price was reduced by 20% to reach £80, the original is NOT £80 + 20% = £96. It's £80 ÷ 0.8 = £100.

Note: Results are rounded to 6 significant figures. For financial calculations always verify with your accountant or financial institution.
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How to Calculate Percentage
Every type of percentage calculation you'll encounter — explained with clear examples.
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// Quick Tricks

To find 10% — move the decimal point one place left. 10% of 350 = 35. Then multiply for other multiples.

// Reverse Sale Price

If an item is on sale at £80 after a 20% discount, the original price is £80 ÷ 0.8 = £100 (not £80 + 20%).

// Percentage Points

"Percentage points" and "percent" are different. Going from 10% to 15% is 5 percentage points but a 50% increase.

// Compound Effect

+20% then −20% does not return to start. 100 → 120 → 96. The order of percentage changes matters!