Percentage Calculator

Solve the three most common percentage questions in one place. Type in any box and the answer updates as you go.

What is X% of Y?
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X is what percent of Y?
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Add or subtract a percentage
Plus the percent–
Minus the percent–
The percent itself–

What a percentage means

"Percent" means "per hundred". 25% is 25 out of every 100, which is the same as the fraction 25/100 or the decimal 0.25. Converting between these forms is the key to every percentage calculation: divide by 100 to turn a percent into a decimal, multiply by 100 to go back.

The three percentage formulas

QuestionFormulaExample
What is P% of X?P ÷ 100 × X15% of 80 = 12
A is what % of B?A ÷ B × 10018 of 24 = 75%
X plus P%X × (1 + P ÷ 100)50 + 8% = 54

Everyday examples

  • Tips: 18% of a $64 bill is 0.18 × 64 = $11.52.
  • Test scores: 42 correct out of 50 is 42 ÷ 50 × 100 = 84%.
  • Sale prices: 30% off $120 is 120 × 0.70 = $84. Use the discount calculator for more detail.
  • Price increases: a $1,500 rent going up 4% becomes 1,500 × 1.04 = $1,560.

Mental math shortcuts

  • 10% is the number with the decimal point moved one place left: 10% of 340 is 34.
  • 5% is half of 10%, and 20% is double 10%.
  • 1% moves the decimal two places: 1% of 340 is 3.4.
  • Swap the numbers when it helps: 8% of 25 is the same as 25% of 8, which is 2.

Comparing an old and new value? The percent change calculator shows increases and decreases.

Last reviewed October 2026.

Frequently asked questions

How do I calculate a percentage of a number?

Turn the percentage into a decimal by dividing by 100, then multiply. 15% of 80 is 0.15 × 80 = 12.

How do I find what percent one number is of another?

Divide the part by the whole and multiply by 100. 18 out of 24 is 18 ÷ 24 × 100 = 75%.

How do I add a percentage to a number?

Multiply by 1 plus the percentage as a decimal. Adding 8% to $50 is 50 × 1.08 = $54. To subtract 8%, multiply by 0.92 instead.

Is 20% of 50 the same as 50% of 20?

Yes. Percentages work both ways because multiplication can be done in any order: 0.20 × 50 = 10 and 0.50 × 20 = 10. This trick makes some mental math easier, such as 4% of 75 = 75% of 4 = 3.

What is the difference between percent and percentage points?

Percentage points measure the plain difference between two percentages. A rate rising from 4% to 5% is up 1 percentage point, but up 25 percent relative to where it started.