Percentage Calculator
Calculate percentages, increases, decreases and percentage difference.
A percentage calculator solves common percentage problems: what is X% of Y, X is what percent of Y, increase or decrease by a percentage, and percentage difference — all with clear formulas.
How to Use the Percentage Calculator
- Choose a calculation. Pick the type of percentage problem.
- Enter the values. Type A and B.
- Read the result. The tool shows the answer with a clear breakdown.
This tool processes your input locally in your browser. Nothing is uploaded.
What Is Percentage Calc?
Percentages appear everywhere — discounts, grades, statistics and finance. A percentage calculator solves the most common calculations instantly and accurately.
What is a percentage?
A percentage is a fraction of 100. "X% of Y" means (X/100) × Y. Percentages are used to express proportions, changes and comparisons.
Key formulas
Percent of a number: (A/100) × B. What percent A is of B: (A/B) × 100. Increase A by B%: A × (1 + B/100). Decrease A by B%: A × (1 − B/100). Percentage difference: |A−B| / ((A+B)/2) × 100.
Common mistakes
A common error is adding a percentage instead of multiplying. For example, increasing 100 by 10% gives 110 (not 110% of 100 confused with 100 + 10). Percentage difference uses the average as the base, not one of the values.
Key Features
- Five common percentage modes
- Clear formulas
- Invalid input validation
- Instant results
Examples
- 15% of 200 = 30.
- 30 is 15% of 200.
- 100 increased by 10% = 110.
- Percentage difference between 100 and 80 is 22.2%.
Common Use Cases
- Discounts
- Grades
- Statistics
- Financial analysis
Tips & Best Practices
- For a 20% discount on a $50 item, the price is 50 × (1 − 0.20) = $40.
- Understand whether a percentage is based on the original or the new value.
Limitations
- Results are exact within standard floating-point precision.