Math
Percentage Calculator
Any percentage problem solved, without fighting the formula
This percentage calculator solves four problems in one: a percent of a number, what percent one number is of another, increases and discounts, and the percent change between two values.
The key idea
Up 20% and then down 20% is not breaking even: it is a 4% loss
If 100 goes up 20%, it becomes 120. If it then drops 20%, it ends at 96. The second percentage applies to a bigger base, so the two do not cancel out. Discounts work the same way: 15% off means multiplying by 0.85.
How it is calculated
- X% of a number: Number × X / 100.
- What % A is of B: A / B × 100.
- Increase or discount: Amount × (1 + X / 100). For a discount, X is negative: 15% off means multiplying by 0.85.
- Percent change: (Final − Starting) / Starting × 100.
Worked example
What is 20% of 150? 150 × 20 / 100 = 30.
Sneakers at $120 with 25% off: 120 × (1 − 0.25) = 120 × 0.75 = $90.
If a price goes from $80 to $92, the change is (92 − 80) / 80 × 100 = +15%.
Watch out: up 20% and then down 20% does not leave you even. 100 → 120 → 96.
Typical cases
Percent of a number chart
What common percentages of common numbers come to, like 20% of 50. To find any other, use the calculator above.
| Percent | Of 50 | Of 80 | Of 150 | Of 200 |
|---|---|---|---|---|
| 5% | 2.50 | 4.00 | 7.50 | 10.00 |
| 10% | 5.00 | 8.00 | 15.00 | 20.00 |
| 15% | 7.50 | 12.00 | 22.50 | 30.00 |
| 20% | 10.00 | 16.00 | 30.00 | 40.00 |
| 25% | 12.50 | 20.00 | 37.50 | 50.00 |
| 30% | 15.00 | 24.00 | 45.00 | 60.00 |
| 40% | 20.00 | 32.00 | 60.00 | 80.00 |
| 50% | 25.00 | 40.00 | 75.00 | 100.00 |
| 60% | 30.00 | 48.00 | 90.00 | 120.00 |
| 75% | 37.50 | 60.00 | 112.50 | 150.00 |
| 80% | 40.00 | 64.00 | 120.00 | 160.00 |
| 90% | 45.00 | 72.00 | 135.00 | 180.00 |
Save or share this table as an image Common questions
Frequently asked questions
How do I find a percent of a number?
Multiply the number by the percent and divide by 100: 20% of 150 is 30. It is the first option in the calculator.
How can I figure out a percentage in my head?
Start from 10%, which means moving the decimal point one place to the left. 5% is half of 10%, 1% is moving the point two places, and 15% is 10% plus 5%.
How do I calculate a discount?
Multiply the price by (1 − discount / 100): 25% off $120 is 120 × 0.75 = $90. In the calculator, choose Apply an increase or discount and enter the percent as a negative number.
How do I calculate the percent increase of a price?
Subtract the starting value from the final value, divide by the starting value and multiply by 100: going from $80 to $92 is +15%. Use the Percent change option.
How do I remove a percentage that is already included in a price?
Divide by (1 + percent / 100). For example, if $107 already includes a 7% tax, the price before tax is 107 / 1.07 = $100. Sales tax rates vary by state and city, so use your own.
What is a percentage point?
It is the difference between two percentages. Going from 10% to 12% is a rise of 2 percentage points, which is a 20% increase.
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