Step-by-step
- Decide which question you are asking from the three on this page.
- For a percentage of a number, multiply the number by the percentage and divide by 100.
- For what percent one number is of another, divide the part by the whole and multiply by 100.
- Enter the values in the Percentage Calculator and check that the result is reasonable.
- For an increase or decrease, use the percentage change guide, which measures from the starting value.
Percentage of a number
15% of 80 is 80 × 15 ÷ 100 = 12. The same result comes from multiplying by 0.15.
What percent is one number of another
If 12 out of 80 passed a test, the share is 12 ÷ 80 × 100 = 15%. Always divide the part by the whole, not the other way round.
Increase and decrease
To add a percentage, multiply by 1 plus the percentage as a decimal: 80 increased by 25% is 80 × 1.25 = 100. To subtract, multiply by 1 minus the percentage: 100 reduced by 20% is 80. Note that going from 80 up to 100 is a 25% rise, while going from 100 back down to 80 is a 20% fall, because each percentage is measured from a different starting value.
Finish the task with DevUtilityKits
Use the relevant online utility, check the result, and continue with your development workflow.
Open Percentage Calculator →Open Percentage Change Calculator →