Percentage Calculator

Solve common percentage questions for prices, grades, tips, changes, comparisons, and other everyday calculations.

Find a percentage of a value
result = percentage ÷ 100 × value
Enter the percentage to apply.
Enter the value that the percentage applies to.

How percentage calculations work

Choose the question that matches what you know, then enter the two values. Percent means “per hundred,” so 20% is the same as 0.20.

Formulas and examples

  • Percentage of a value: 20% of 150 is 20 ÷ 100 × 150 = 30.
  • One value as a percentage: 30 is 30 ÷ 120 × 100 = 25% of 120.
  • Percentage change: a change from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%.
  • Reverse percentage: if 120 is the value after a 20% increase, the original is 120 ÷ 1.20 = 100.

Percentage change needs a starting value greater than zero. A starting value of zero has no finite percentage baseline. In reverse mode, enter increases as positive percentages and decreases as negative percentages.

Everyday percentages and solution dilutions are different

This calculator handles general percent math. For changing the concentration of a laboratory solution, use the Solution Dilution Calculator, which accounts for concentration and volume.