Percentage Calculator

Three calculators - find a percentage, a value, or a percentage change.

Stays in your browser · Always free

This free percentage calculator covers the three most common percentage problems: finding what percent one number is of another, calculating X% of a value, and working out percentage increase or decrease.

Common uses:

Calculate a tip or service charge on a restaurant bill
Find the discount amount on a sale item
Work out grade percentages or score differences

What is X% of Y?

What is % of ?

X is what % of Y?

is what % of ?

Percentage change from X to Y

From to

The three calculators above cover every percentage problem you're likely to run into: finding a percent of a number, expressing one number as a percentage of another, and calculating the percentage change between two values. Same underlying operation - division and multiplication by 100 - applied to different starting questions.

How percentages work

A percentage is just a fraction with a fixed denominator of 100. 20% means 20/100 means 0.20. Once you have that, every percentage problem reduces to multiplication or division.

X% of Y = (X / 100) × Y X is what % of Y = (X / Y) × 100 % change = ((new − old) / old) × 100

The most common mistake is dividing by the wrong value when calculating change. Always divide by the original number, not the new one. Going from 100 to 80 is a 20% decrease (20/100); going from 80 back to 100 is a 25% increase (20/80). The percentages are not symmetric - that catches people out constantly.

The second common mistake is confusing percentage points with percent. If a tax rate goes from 4% to 6%, that's a 2-percentage-point increase but a 50% relative increase. Both descriptions are valid; people just need to use the same one consistently.

Real-world examples

Sale price

$129 jacket, 35% off. The discount is 0.35 × 129 = $45.15; the sale price is $129 − $45.15 = $83.85.

Tipping

$87 bill, 20% tip. Tip = 0.20 × 87 = $17.40; total = $104.40. For a quick mental shortcut: 20% is double 10%, and 10% is just shifting the decimal.

Salary increase

From $72,000 to $78,000 is a (78,000 − 72,000) / 72,000 = 0.0833 = 8.33% raise. Going the other way, a $6,000 cut from $78,000 would be 6,000 / 78,000 = 7.69%.

Tax-inclusive vs tax-exclusive

If a $108 receipt includes 8% sales tax, the pre-tax price is 108 / 1.08 = $100, and the tax is $8. Common mistake: subtracting 8% of $108 ($8.64) from $108, which gives $99.36 - the wrong answer.

Frequently asked questions

How do I calculate what percent X is of Y?

Divide X by Y and multiply by 100. For example, 30 is what % of 200? 30 ÷ 200 × 100 = 15%. Use the "X is what % of Y?" calculator above.

How do I find X% of a number?

Multiply the number by X divided by 100. For example, 20% of 150 = 150 × 0.20 = 30. Use the "What is X% of Y?" calculator above.

How do I calculate percentage increase?

Subtract the original value from the new value, divide by the original, then multiply by 100. Formula: ((New − Old) ÷ Old) × 100. For example, from 80 to 100: ((100 − 80) ÷ 80) × 100 = 25%.

How do I calculate percentage decrease?

Same formula as percentage change: ((New − Old) ÷ Old) × 100. A negative result means a decrease. For example, from 100 to 75: ((75 − 100) ÷ 100) × 100 = −25%.

What is 15% of 200?

15% of 200 = 200 × 0.15 = 30.

How do I calculate a tip percentage?

Use the "What is X% of Y?" calculator. Enter the tip percentage (e.g. 18) and the bill total. For a $65 bill with 18% tip: 18% of 65 = $11.70.

Why isn't a 20% discount followed by a 20% increase the same as the original price?

Because the percentages apply to different bases. A 20% discount on $100 is $80. A 20% increase on $80 is $96, not $100. The increase is calculated on the smaller number. To get back to $100 from $80, you'd need a 25% increase.

What's the difference between percent and percentage points?

Percentage points are absolute differences between two percentages; percent is a relative change. If interest rates rise from 4% to 6%, that's a 2-percentage-point increase or a 50% relative increase - both are correct, but they describe different things. Financial reporting often confuses the two.

Percentage Calculator

Related tools