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Percentage Calculator

Three everyday percentage problems, solved instantly.

What is X% of Y?

% of

Answer: 30

X is what percent of Y?

is what % of

Answer: 75%

Percentage change (increase / decrease)

Answer: 25% increase

How percentage calculations work

A percentage is simply a fraction of 100. Every percentage problem is one of three questions. "What is X% of Y?" — multiply: Y × X ÷ 100. So 20% of $150 is $150 × 20 ÷ 100 = $30. This is the math behind tips, taxes, discounts, and commissions.

"X is what percent of Y?" — divide the part by the whole: X ÷ Y × 100. If you got 45 out of 60 on a test, that's 45 ÷ 60 × 100 = 75%. This is the formula behind grades, completion rates, and body-fat-style ratios.

"What is the percentage change?" — take the difference, divide by the starting value: (New − Old) ÷ Old × 100. A stock moving from $40 to $50 rose 25%. Note the direction matters: going from $50 back to $40 is a 20% decrease, not 25% — the base changed. That asymmetry trips people up constantly with discounts and markups.

Example: A jacket marked $120 is 30% off. Discount = $120 × 30 ÷ 100 = $36, so you pay $84. If the store then adds 8% sales tax: $84 × 8 ÷ 100 = $6.72, total $90.72.

Percentage FAQs

How do you calculate X percent of Y?

Multiply Y by X and divide by 100. Example: 20% of 150 = 150 × 20 ÷ 100 = 30.

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

Divide the part by the whole and multiply by 100. Example: 45 ÷ 60 × 100 = 75%.

How do you calculate percentage increase?

(New − Old) ÷ Old × 100. A price rising from $40 to $50 is a 25% increase. Remember the reverse trip uses a different base: $50 back to $40 is a 20% decrease.