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Percentage Calculator
This percentage calculator puts six everyday percentage sums in one place. Fill in the blanks and the answer appears straight away, with the working shown underneath.
Calculators
Results are rounded to 4 decimal places. Percentage difference compares two values against their average; use percentage change when one value is the starting point.
Percentage formulas
A percentage is a number out of 100, so 20% means 20 ÷ 100 = 0.2. Every calculator above is one of these formulas.
| Calculation | Formula | Example |
|---|---|---|
| Percent of a number | result = P ÷ 100 × X | 20% of 150 = 0.2 × 150 = 30 |
| What percent A is of B | percent = A ÷ B × 100 | 30 ÷ 150 × 100 = 20% |
| Percentage change | change = (new − old) ÷ |old| × 100 | 80 → 100: 20 ÷ 80 × 100 = +25% |
| Increase or decrease by P% | result = X × (1 ± P ÷ 100) | 150 + 20% = 150 × 1.2 = 180 |
| Find the whole | whole = A ÷ (P ÷ 100) | 30 is 20% of → 30 ÷ 0.2 = 150 |
| Percentage difference | difference = |A − B| ÷ ((A + B) ÷ 2) × 100 | 80 and 100: 20 ÷ 90 × 100 = 22.22% |
Quick mental shortcuts
10% is a decimal shift
Move the decimal point one place left: 10% of 240 is 24. Halve it for 5% (12), double it for 20% (48).
Percentages swap round
X% of Y equals Y% of X. 8% of 50 is hard; 50% of 8 is 4 — and it's the same answer.
Use a multiplier
Adding 15% is multiplying by 1.15; taking off 15% is multiplying by 0.85. Chain them for repeated changes.
Frequently asked questions
How do I calculate a percentage of a number?+
Divide the percentage by 100 and multiply by the number. For 15% of 80: 15 ÷ 100 = 0.15, and 0.15 × 80 = 12.
How do I work out a percentage increase or decrease?+
Subtract the old value from the new one, divide by the old value and multiply by 100. Going from 50 to 65 is (65 − 50) ÷ 50 × 100 = 30%, an increase. A negative answer is a decrease.
What is the difference between percentage change and percentage difference?+
Percentage change has a direction: it measures from a starting value to a new one. Percentage difference compares two values with no starting point, dividing the gap by their average, so it is the same whichever way round you enter them.
Why doesn't a 20% increase followed by a 20% decrease get me back to where I started?+
Because the second percentage is taken of a bigger number. 100 + 20% is 120, and 120 − 20% is 96. To undo a 20% increase you need a decrease of about 16.67%.
How do I find the original price before a discount?+
Use “Find the whole”. If an item costs 68 after a 15% discount, you paid 85% of the original, so enter 68 is 85% of what — the answer is 80.
What is a percentage point?+
The plain difference between two percentages. An interest rate going from 4% to 5% rises by 1 percentage point, which is a 25% increase in the rate itself.
How do I work out a test score as a percentage?+
Divide the marks you got by the total marks and multiply by 100. 18 out of 24 is 18 ÷ 24 × 100 = 75%. Use “What percent one number is of another” and enter 18 and 24.
How do I add sales tax or VAT to a price?+
Multiply the price by 1 plus the rate as a decimal. 80 plus 8.25% sales tax is 80 × 1.0825 = 86.60; 50 plus 20% VAT is 50 × 1.2 = 60. Use “Increase or decrease by a percentage” and choose increased by.
How do I take a percentage off a price?+
Multiply the price by 1 minus the discount as a decimal. 60 with 25% off is 60 × 0.75 = 45, a saving of 15. Use “Increase or decrease by a percentage” and choose decreased by.
Can a percentage increase be more than 100%?+
Yes. An increase of 100% doubles the starting value, so going from 40 to 100 is a 150% increase. A decrease of a positive amount can't go beyond −100%, which would mean falling to zero.
Can I use decimals, negative numbers or commas?+
Yes. You can type decimals such as 12.5 (or 12,5), thousands separators such as 1,250 or 1,25,000, a minus sign and a trailing % sign. Percentage change from a negative starting value is measured against its size, so −50 to −25 is a 50% increase.
Is anything I type stored or sent anywhere?+
No. Every calculation runs in your browser and nothing is saved or uploaded.
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