Percentage Calculator

The formula

A percentage expresses a part as a fraction of 100. To find what percent a value is of a total:

Percentage = value ÷ total × 100

Example: you scored 45 points out of 60. 45 ÷ 60 = 0.75, and 0.75 × 100 = 75%.

The three classic percentage questions

This calculator answers the first question. For the second, multiply the total by the percentage and divide by 100 — or use the discount and tip calculators, which do it for prices. For changes between two values, use the percentage increase and decrease calculators.

Quick mental tricks

• 10%: move the decimal point one place left (10% of 340 = 34). Then 5% is half of that, 20% is double.
• 1%: move it two places (1% of 340 = 3.4), useful to build any percentage: 7% = 7 × 3.4 = 23.8.
• Swap trick: x% of y equals y% of x. 8% of 50 is the same as 50% of 8, which is 4.

Common mistakes

• Percentages are not symmetric. A price that rises by 50% and then falls by 50% does not return to its starting point: 100 → 150 → 75.
• Percent vs percentage points. If an interest rate goes from 2% to 3%, it rose by 1 percentage point, but by 50% in relative terms.
• Using the wrong base. "A is 25% more than B" and "B is 25% less than A" are not the same statement: if B = 100 and A = 125, B is only 20% less than A.
• Adding percentages of different totals. 10% of one class plus 20% of another is not 30% of all students unless the classes are the same size.

Formulas and content last reviewed: October 2026 · About