Percentage Calculator
Everyday percentage jobs: of, what percent, change, increase, and decrease. Figures stay on this device.
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How to calculate a percentage
- Pick the job: of, what percent, of-what, change, increase, or decrease.
- Fill the fields that appear for that job.
- Of-what answers '30 is 15 percent of what'.
- Nothing is uploaded.
Percentage
Ratio of a part to a whole, times 100
| Of | P/100 × X |
|---|---|
| What percent | 100 × part / whole |
| Change | 100 × (new − original) / original |
| Increase or decrease | X × (1 ± P/100) |
What a percentage is
A percentage is a ratio times 100. 15% of 200 is 30. If 30 is the part and 200 is the whole, the percent is 15. Percent change from 80 to 100 is 25%. Increase and decrease apply a percent to a starting amount and return the new amount.
Which job to pick
Use of when you already have the percent. Use what percent when you have two amounts. Use change when a value moved from one number to another. Increase and decrease apply a percent to a starting amount. Change also reports the raw difference.
Formulas this page uses
Of: (P / 100) × X. What percent: 100 × part / whole. Change: 100 × (new − original) / original. Increase: X × (1 + P/100). Decrease: X × (1 − P/100). Percent change is undefined when the original is 0.
Tips, tax, and stacked percents
A restaurant tip is the same arithmetic as increase. The tip calculator also splits a bill. A 15% decrease then a 15% increase is not the original: 100 becomes 85, then 97.75. Sales tax that needs a jurisdiction table is not on this page.