Percentage Calculator
Use this free percentage calculator to work out everyday percentage problems without remembering which formula to use. Pick a calculation type — a percentage of a number, what percentage one number is of another, a percentage increase or decrease, a percentage difference, a percentage of a percentage, or percentage points — enter your numbers, and get a clear result plus the exact equation behind it.
It is built for students checking test scores, shoppers working out discounts and markups, and analysts comparing figures. Every calculation runs locally in your browser, so your numbers never leave your device, and you can see the formula that produced each answer.
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How to Use the Percentage Calculator
Choose the calculation type that matches your problem.
Enter the required values in the labelled fields.
Click "Calculate" or press Enter.
Review the result and the formula shown beneath it.
Copy the result if you need to use it elsewhere.
What Is a Percentage?
A percentage is a way of expressing a number as a fraction of 100. The word comes from "per cent", meaning "per hundred", so 25% literally means 25 out of 100, or the fraction 25/100, which is also the decimal 0.25.
Because a percentage is just a fraction with a denominator of 100, it moves easily between forms: 50% = 50/100 = 1/2 = 0.5. That relationship is why most percentage calculations are really fraction or decimal calculations in disguise — divide by 100 to turn a percent into a decimal, multiply by 100 to turn a decimal back into a percent.
How to Calculate a Percentage
- Part of a whole: To find what percentage one number is of another, divide the part by the whole and multiply by 100: part ÷ whole × 100.
- Example: 30 out of 200 is (30 ÷ 200) × 100 = 15%.
- Percentage of a number: To take X% of Y, convert the percent to a decimal and multiply: X ÷ 100 × Y.
How to Calculate Percentage Increase or Decrease
- The formula: Subtract the original from the new value, divide by the original, then multiply by 100: (new − original) ÷ original × 100.
- Direction: A positive result is an increase; a negative result is a decrease. The absolute difference (new − original) tells you the raw change in units.
- Example: 100 to 125 is (125 − 100) ÷ 100 × 100 = 25% increase; 100 to 80 is a 20% decrease.
Percentage Change vs Percentage Difference
- Change: Percentage change measures movement from one specific baseline (the original value) to a new value.
- Difference: Percentage difference treats both values equally, using their average as the baseline: |A − B| ÷ ((A + B) ÷ 2) × 100.
- Why it matters: Use change when one value is clearly the "before"; use difference when neither is a baseline, such as comparing two independent measurements.
Percentage Points vs Percentage Increase
- Percentage points: A percentage point is the simple arithmetic difference between two percentages. 5% to 7% is a move of 2 percentage points.
- Relative increase: The same move is also a 40% relative increase, because 2 is 40% of the starting 5%. Mixing these up is a common mistake.
- Example: If interest rises from 5% to 7%, say "up 2 percentage points", not "up 2%", which would wrongly imply 5% to 5.1%.
Reverse Percentages
- Finding the original: If you know a result and the percentage it represents, divide the result by the percentage as a decimal to recover the whole.
- Example: 50 is 25% of what number? 50 ÷ (25 ÷ 100) = 200.
- Use case: Handy for working backwards from a discounted price to the original, or from a taxed amount to the pre-tax figure.
Common Percentage Mistakes
- Points vs percent: Treating a 2-point rise as a 2% rise overstates or understates the real change depending on the starting value.
- Wrong baseline: Dividing by the new value instead of the original flips a percentage change calculation.
- Forgetting the decimal: Using 25 instead of 0.25 turns "25%" into something 100 times too large in a multiplication.
Frequently Asked Questions
How do I calculate a percentage?
To find what percentage X is of Y, divide X by Y and multiply by 100. To take X% of a number, divide X by 100 and multiply by that number. The calculator shows both the answer and the equation it used.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide the result by the original value, and multiply by 100. A positive result is an increase; a negative result is a decrease.
What is the difference between percentage change and percentage difference?
Percentage change compares a new value to a specific original baseline. Percentage difference compares two values as equals, using their average as the baseline, which is useful when neither value is clearly "before" the other.
How do I find the original number from a percentage?
Divide the known result by the percentage expressed as a decimal. For example, if 50 is 25% of a number, divide 50 by 0.25 to get 200.
What is the difference between percentage points and percentage?
A percentage point is the straight difference between two percentages (5% to 7% is 2 percentage points). The relative change between those same values is 40%, because 2 is 40% of 5. They describe the same move in different ways.
Can I use this percentage calculator for discounts?
Yes. To find a discount amount, calculate the percentage of the original price; to find the final price after a percentage decrease, use the percentage change mode or subtract the discount from the original.
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