Percentage Calculator
Calculate percentages instantly — percentage of a number, percentage change, increase or decrease, and reverse percentages. Free, mobile-friendly, no sign-up.
Disclaimer: This calculator is provided for informational and educational purposes only. It does not constitute financial, tax, or professional advice.
What is a percentage?
A percentage is a number expressed as a fraction of 100. The word comes from the Latin "per centum", meaning "by the hundred". Percentages are used everywhere — from discounts and interest rates to test scores and statistics — because they make it easy to compare proportions on a common scale.
The symbol for percentage is %. When you see "25%", it means 25 out of 100, or 25/100, or 0.25 in decimal form. To convert a decimal to a percentage, multiply by 100. To convert a percentage to a decimal, divide by 100.
How to calculate a percentage of a number
To find a percentage of a number, multiply the number by the percentage divided by 100. For example, to find 15% of 200:
15 ÷ 100 × 200 = 0.15 × 200 = 30
So 15% of 200 is 30. This is useful for calculating discounts, tips, tax, and commission.
How to calculate percentage change
Percentage change measures how much a value has increased or decreased relative to its original value. The formula is:
Percentage change = (New value − Original value) ÷ Original value × 100
If the result is positive, it's an increase. If negative, it's a decrease. For example, if a stock rises from $50 to $65, the percentage change is (65 − 50) ÷ 50 × 100 = 30% increase.
Common percentage calculations
Percentages are used in many everyday situations:
- **Discounts**: A $80 item at 25% off costs $80 × (1 − 0.25) = $60.
- **Tax**: 10% GST on a $150 purchase adds $15.
- **Tips**: An 18% tip on a $45 meal is $8.10.
- **Interest**: 5% annual interest on $1,000 earns $50 per year.
- **Grades**: Scoring 42 out of 50 is 42 ÷ 50 × 100 = 84%.
Frequently Asked Questions
How do I calculate percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 20% of 150 = 150 × 20 ÷ 100 = 30.
How do I calculate percentage increase?
Use the formula: ((New − Original) ÷ Original) × 100. If a price goes from $40 to $50, the increase is ((50−40)÷40)×100 = 25%.
How do I calculate percentage decrease?
Use the same formula as increase. If a price drops from $50 to $40, the decrease is ((40−50)÷50)×100 = −20%, or a 20% decrease.
What is the difference between percentage and percentile?
A percentage is a fraction of 100. A percentile is the value below which a certain percentage of data falls. Scoring in the 90th percentile means you scored better than 90% of people.
How do I convert a decimal to a percentage?
Multiply by 100. For example, 0.75 × 100 = 75%.