Percentage Calculator
Find what percent one number is of another, a percentage of a number, percent change, the result of adding or taking off a percentage, the original value before a percentage was applied, and the overall change after several steps.
What percentage of the Whole is the Part?
How to use the Percentage Calculator
- Pick a mode at the top: what percent one number is of another, a percentage of a number, percent change, adding or taking off a percentage, finding the original value, or successive changes.
- Fill in the fields. Decimals and negative numbers are accepted.
- The answer and the working appear as you type. Change the number of decimals under the result if you need more or fewer.
- Each result is added to Recent calculations, and the link button copies an address that opens the same calculation for someone else.
The six modes and their formulas
| Mode | Formula | Example |
|---|---|---|
| X is what % of Y | Part รท Whole ร 100 | 25 of 200 is 12.50% |
| X% of a number | Number ร Percent รท 100 | 15% of 80,000 is 12,000 |
| Percent change | (To โ From) รท From ร 100 | 80 to 100 is a 25.00% increase |
| Add or subtract % | Number ร (1 ยฑ Percent รท 100) | 50,000 plus 10% is 55,000; minus 10% is 45,000 |
| Original after an increase | Value รท (1 + Percent รท 100) | 110 after a 10% rise was 100 |
| Original after a decrease | Value รท (1 โ Percent รท 100) | 80 after 20% off was 100 |
| Whole from a part | Part รท Percent ร 100 | If 15% is 12,000, the whole is 80,000 |
| Successive changes | Start ร (1 + first รท 100) ร (1 + second รท 100) โฆ | Up 10% then down 10% is a 1.00% decrease |
Percentages show two decimal places and other results up to four unless you pick a different setting under the result, so 1 out of 3 shows as 33.33%.
Finding the original value
Taking the same percentage back off does not undo an increase. A price of 110 that already includes 10% was 100 before, which is 110 รท 1.1, while 110 minus 10% gives 99. The percentage was worked out on the original, so you have to divide rather than subtract. A discount works the same way: 80 after 20% off was 80 รท 0.8 = 100.
Successive changes do not simply add up
A 10% rise followed by a 10% fall leaves you 1% down, because the second change is taken from the larger number. Two rises of 20% and 30% add up to 56%, not 50%. Enter the changes in order, separated by commas, and the calculator shows the value after each step and the overall percentage.
Zero totals and negative values
A Whole of zero, or a From value of zero in percent change, has no answer, so a warning replaces the number instead of printing infinity. Negatives pass through and keep their sign, which is why a Part of -25 against a Whole of 200 returns -12.50%. Percent change divides by the size of the From value, so a move from -50 to -25 reads as an increase.
Frequently asked questions
What if the total is zero?
Dividing by zero is undefined, so a warning is shown instead of a result. The same applies when the From value is zero in percent change.
Can I use negative numbers?
Yes, negative values are calculated as entered.
How do I work out 15% of a number?
Choose the X% of a number mode, then enter the number and 15 as the percent. For 200 the answer is 30, which is 200 ร 15 รท 100.
Can it give me a percentage increase?
Yes. Choose Percent change and enter the old value as From and the new value as To. Going from 80 to 100 returns a 25.00% increase.
How do I find the price before tax or a discount?
Choose Find the original, pick after an increase or after a decrease, and enter the final value and the percentage. A total of 110 including 10% was 100 before, and 80 after 20% off was 100.
Does a 10% rise and a 10% fall cancel out?
No. You end up 1% lower, because the fall is taken from the higher value. Enter 10, -10 in Successive changes to see each step.
Can I change the number of decimal places?
Yes. Pick 0 to 4 decimals under the result. On Auto, percentages show two places and other values up to four.