Calculate percentages instantly: find X% of a number, what percentage X is of Y, or the percentage change between two values.
Percentage Calculator
Result
Result
% Change
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How to Calculate Percentages
A percentage is a fraction expressed as a part of 100. The word comes from the Latin per centum, meaning "per hundred." Percentages appear everywhere — discounts, tax rates, interest rates, test scores, and statistics.
Three Common Percentage Formulas
X% of Y: Result = (X ÷ 100) × Y — e.g. 20% of 500 = 100
X is what % of Y: Percentage = (X ÷ Y) × 100 — e.g. 50 is 25% of 200
% Change from A to B: Change = ((B − A) ÷ |A|) × 100 — a positive result is an increase, negative is a decrease
Common Percentage Examples
Question
Formula
Answer
15% of 80
0.15 × 80
12
30 is what % of 120
(30 ÷ 120) × 100
25%
Price rises from $80 to $100
((100−80) ÷ 80) × 100
+25%
Score: 45 out of 60
(45 ÷ 60) × 100
75%
Tips for Quick Mental Math
10%: Move the decimal point one place left — 10% of 350 = 35
5%: Half of 10% — 5% of 350 = 17.5
1%: Move the decimal two places left — 1% of 350 = 3.50
25%: Divide by 4 — 25% of 200 = 50
33.3%: Divide by 3 — 33% of 300 = 100
Frequently Asked Questions
Multiply the original price by 0.20 to find the discount, then subtract from the original. Example: 20% off $85 = $85 × 0.20 = $17 discount, so you pay $68. Alternatively, multiply by 0.80 directly: $85 × 0.80 = $68.
Percentage increase = ((New Value − Old Value) ÷ Old Value) × 100. If a salary goes from $50,000 to $55,000, the increase is ((55,000 − 50,000) ÷ 50,000) × 100 = 10%.
Divide the sale price by (1 − discount%). For example, if an item is $60 after a 25% discount: original price = $60 ÷ 0.75 = $80.
These are different. If an interest rate rises from 2% to 3%, it rose by 1 percentage point — but by 50% relative to its original value. Confusing the two is a common error in financial reporting.