Percentage calculator: percent of, percent change, add or subtract a percentage

Calculation
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About the percentage calculator

This calculator handles the percentage questions that come up most: what is X% of Y, what percent one number is of another, how much a value changed in percent, how far apart two values are, what a number becomes after adding or subtracting a percentage, and what the original number was before a percentage was applied. Pick the calculation, type two numbers, and the result appears with the formula worked through step by step. Decimals and negative numbers work, and if a calculation would divide by zero you get a plain message instead of a wrong answer.

How to calculate a percentage

  1. Choose the calculation from the menu, for example X% of Y or Percentage change.
  2. Type your two numbers. The result updates as you type.
  3. Read the steps under the result to see how it was worked out.
  4. Press the copy button to copy the result or the full working.

Frequently asked questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. 15% of 200 is 15 / 100 × 200 = 30. Pick X% of Y, enter both numbers and the steps are shown.

How do I find what percent one number is of another?

Divide the part by the whole and multiply by 100. 30 is 30 / 200 × 100 = 15% of 200. The whole can't be 0, because dividing by zero is undefined.

How do I calculate percentage change?

Subtract the old value from the new one, divide by the old value and multiply by 100. Going from 80 to 100 is (100 - 80) / 80 × 100 = 25% increase. Going from 100 to 80 is a 20% decrease, which is why the two directions are not symmetrical.

What is the difference between percentage change and percentage difference?

Percentage change has a clear starting point: it compares a new value to an old one. Percentage difference has none, so it divides the gap by the average of the two values. Swapping the values gives the same answer. Use change for before and after, and difference for two things you are comparing.

How do I add or subtract a percentage from a number?

Work out the percentage of the number and add it or take it away. 20% added to 50 is 50 + 10 = 60. In one step, multiply by 1.20. To subtract 20%, multiply by 0.80 instead. This is how discounts, tax and tips are worked out.

How do I find the original number before a percentage change?

Divide the result by the change factor. If a price is 60 after a 20% increase, the original is 60 / 1.20 = 50. After a 20% decrease, divide by 0.80. If a number is 25% of something, divide it by 0.25 to find the whole.

Why is a 50% increase followed by a 50% decrease not back to the start?

Each percentage applies to a different base. 100 plus 50% is 150, and 50% of 150 is 75, so you end at 75. To undo an increase of 50% you need a decrease of about 33.3%.

What happens when I divide by zero or use negative numbers?

Percentages involving a zero whole, zero start value or zero average are undefined, so the calculator shows a message instead of a number. Negative numbers and decimals work in every mode. For percentage change, a negative starting value is divided by its absolute value so that a rise always shows as an increase.

Is my data sent anywhere?

No. Everything is calculated in your browser and nothing is uploaded. Your numbers are kept in the page address so you can bookmark or share a calculation.