Percentage Calculator
Calculate percentages, percentage change and percentage ratios instantly.
How to calculate a percentage
A percentage expresses a number as a fraction of 100. To find X% of a number Y, multiply Y by X and divide by 100 — for example, 20% of 150 is (20 × 150) / 100 = 30. This calculator handles the three most common percentage questions people search for: finding a percentage of a value, finding what percent one number is of another, and finding the percentage increase or decrease between two values.
Percentage change formula
Percentage change is calculated as ((New Value − Old Value) / Old Value) × 100. A positive result means an increase, while a negative result means a decrease. This is useful for tracking price changes, salary raises, weight loss, business growth, and exam score improvements.
Common uses
- Calculating discounts and sale prices while shopping
- Working out grade percentages from test scores
- Tracking growth or decline in business metrics
- Splitting commissions, taxes, or tips
Frequently asked questions
What's the difference between percentage change and percentage of a number?
"Percentage of a number" answers questions like "what is 20% of 150?" A "percentage change" answers "by what percent did a value increase or decrease?" - for example, going from 80 to 100 is a 25% increase, not a 20% increase, because the change is measured relative to the original value.
Why is percentage increase and decrease not symmetric?
Because each is calculated relative to a different starting number. A 50% increase from 100 gives 150, but a 50% decrease from 150 only brings you back to 75, not 100 - the base value changes between the two calculations.
How do I calculate what percentage one number is of another?
Divide the part by the whole and multiply by 100 - for example, 45 out of 60 is (45 / 60) x 100 = 75%. Use the relevant mode in the calculator and enter both numbers to get this instantly.