Percentage Calculator
Solve the three most common percentage problems: find a percentage of a number, determine what percent one number is of another, and calculate percentage change between two values.
Formula: (X ÷ 100) × Y
Formula: (X ÷ Y) × 100
Formula: ((New − Old) ÷ Old) × 100
How to use the Percentage Calculator
Choose the type of percentage problem from the three tabs above, fill in the known values, and the answer appears immediately. Switch between modes at any time.
How percentage calculations work
X% of Y: Result = (X ÷ 100) × Y. Example: 20% of 150 = 30.
X is what % of Y: Result = (X ÷ Y) × 100. Example: 30 is what % of 150 = 20%.
Percentage change: Result = ((New − Old) ÷ Old) × 100. A positive result is an increase; negative is a decrease.
Frequently Asked Questions
How do I find 15% of a number?
Multiply the number by 0.15. For example, 15% of 200 = 200 × 0.15 = 30. You can also find 10% first (move the decimal one place left), then add half of that to get 15%. Example: 10% of 200 = 20, half = 10, so 15% = 30.
What is the difference between percentage and percentage points?
A percentage is a fraction of 100 (e.g., an interest rate of 5%). A percentage point is an arithmetic difference between two percentages. If rates rise from 5% to 7%, that is a 2 percentage-point increase, but a 40% relative increase.
How do I calculate a percentage increase?
Subtract the original value from the new value, divide the result by the original value, then multiply by 100. Example: price rose from $40 to $50 → ((50 − 40) ÷ 40) × 100 = 25% increase.
How do I reverse a percentage — for example, find the original price before a 20% discount?
Divide the discounted price by (1 − discount rate). Example: sale price is $80 after a 20% discount → original price = $80 ÷ 0.80 = $100. Do not simply add 20% back — that gives the wrong answer.
What does a negative percentage change mean?
A negative percentage change means the value decreased. For example, going from 100 to 75 is a −25% change, meaning a 25% decrease. The sign tells you the direction; the number tells you the magnitude.