Percentage Calculator
Choose the type of percentage calculation you need.
What is X% of Y?
Result
X is what % of Y?
Result
Percentage increase / decrease
Percentage Change
How to Calculate Percentages
A percentage is a fraction of 100. To find X% of Y, multiply Y by X and divide by 100. For example, 15% of 80 = (80 × 15) ÷ 100 = 12. To find what percent X is of Y, divide X by Y and multiply by 100 — so 30 out of 200 is (30 ÷ 200) × 100 = 15%.
Percentage change measures how much a value has grown or shrunk relative to its starting point. The formula is ((New − Old) ÷ Old) × 100. A positive result is an increase; a negative result is a decrease. This is useful for comparing prices, tracking statistics, or evaluating performance over time.
Common Percentage Examples
| Question | Answer |
|---|---|
| What is 15% of 200? | 30 |
| What is 8% of $45? | $3.60 |
| 25 is what percent of 200? | 12.5% |
| Price went from $80 to $100 — what % increase? | 25% |
| Price dropped from $120 to $90 — what % decrease? | −25% |
Frequently Asked Questions
How do I calculate a percentage in my head?
For quick mental math: 10% is always easy (move decimal left one place). Build from there: 5% = half of 10%, 20% = double 10%, 15% = 10% + 5%, 25% = divide by 4. Example: 15% of $60 = $6 + $3 = $9.
What’s the difference between percentage and percentage points?
These are easily confused. If an interest rate goes from 4% to 5%, it rose by 1 percentage point, but it rose by 25% (1 ÷ 4 = 25%). Percentage points describe absolute changes in percentages; percentages describe relative changes.
How do I calculate a percentage increase?
Use the formula: ((New Value − Old Value) ÷ Old Value) × 100. If your salary went from $50,000 to $55,000: (($55,000 − $50,000) ÷ $50,000) × 100 = 10% increase. Use the “% Change” tab above for instant results.
What is 100% of something?
100% of any number is the number itself. 200% of a value is double it. 50% is half. Percentages above 100% mean the result is larger than the original value — for example, a 150% increase means the value grew by 1.5 times its original amount.
How do I reverse a percentage to find the original number?
If you know a final value and the percentage applied, divide by the percentage as a decimal. If a price is $78 after a 20% increase: $78 ÷ 1.20 = $65 original. If it’s $78 after a 20% decrease: $78 ÷ 0.80 = $97.50 original.