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Percentage Calculator
Six everyday percentage calculators 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.
Is anything I type stored or sent anywhere?+
No. Every calculation runs in your browser and nothing is saved or uploaded.