Calculate percentages of a number, find what percent one value is of another, measure percent change, and solve reverse percent problems.
- Percent Decrease Calculator
- Percent Growth Calculator
- Reverse Percentage Calculator
- All Math and Numbers Calculators
Percentage Formula
The calculator uses a different formula for each tab.
Percent of a number:
Result = (P / 100) * V
X is what % of Y:
Percent = (X / Y) * 100
Percent change:
Change% = ((Vf - Vi) / |Vi|) * 100
Tip or discount:
Total = Price ± (Price * P / 100)
- P — percent
- V — base value
- X — the part
- Y — the whole
- Vi — starting (initial) value
- Vf — ending (final) value
- Price — bill or sticker price before tip or discount
Y cannot be zero in the X-of-Y mode. Starting value cannot be zero in percent change mode. Percent change uses the absolute value of the starting number, so a drop from -10 to -5 is reported as a positive change.
Common Percentages and Reference Tables
Use these to sanity-check a result before you trust it.
| Percent | Decimal | Fraction | Of 100 | Of 250 |
|---|---|---|---|---|
| 5% | 0.05 | 1/20 | 5 | 12.5 |
| 10% | 0.10 | 1/10 | 10 | 25 |
| 15% | 0.15 | 3/20 | 15 | 37.5 |
| 20% | 0.20 | 1/5 | 20 | 50 |
| 25% | 0.25 | 1/4 | 25 | 62.5 |
| 33.33% | 0.3333 | 1/3 | 33.33 | 83.33 |
| 50% | 0.50 | 1/2 | 50 | 125 |
| 75% | 0.75 | 3/4 | 75 | 187.5 |
Tipping ranges in the United States, for context:
| Service | Standard Tip |
|---|---|
| Sit-down restaurant | 18% to 20% |
| Takeout / counter | 0% to 10% |
| Food delivery | 15% to 20% |
| Taxi or rideshare | 10% to 15% |
| Hair stylist or barber | 15% to 20% |
Worked Examples
1. What is 18% of 240?
0.18 × 240 = 43.2
2. 27 is what percent of 60?
(27 ÷ 60) × 100 = 45%
3. A stock moves from 80 to 92. What is the percent change?
((92 − 80) ÷ 80) × 100 = +15%
4. A $64 bill with a 20% tip.
64 + (64 × 0.20) = 76.80
Why does percent change use the starting value, not the ending one? Percent change measures growth relative to where you began. Switching the denominator to the ending value gives a different number and answers a different question.
Can a percent be greater than 100? Yes. If X is larger than Y, the result will exceed 100%. A value that doubles has increased by 100%; one that triples has increased by 200%.
Discount versus markup. A 20% discount on $50 gives $40. A 20% markup on $40 gives $48, not $50. Adding a percent and removing the same percent are not inverse operations because the base changes.
