Percentage Calculator

Calculate percentages, percentage increases/decreases, and find what percent one number is of another. Perfect for discounts, taxes, tips, and more.

How to Use This Calculator

Select the type of percentage calculation you need from the dropdown menu
Enter the first value in the "First Value" field
Enter the second value in the "Second Value" field
Adjust the decimal places slider if you need more or less precision
Click Calculate to see your results

Formula Used

Percentage = (Part / Whole) × 100

Where:

Part = The portion or amount you're calculating the percentage for
Whole = The total amount or reference value
Percentage = The result expressed as a percentage

Additional Formulas:

X% of Y = (X/100) × Y
X is what percent of Y = (X/Y) × 100
X is Y% of what = X/(Y/100)
Percentage Increase = ((New Value - Original Value) / Original Value) × 100
Percentage Decrease = ((Original Value - New Value) / Original Value) × 100

Example Calculation

Real-World Scenario:

You want to calculate a 20% discount on a $150 item and determine the final price after the discount.

Given:

Original Price = $150
Discount Percentage = 20%

Calculation:

Discount Amount = (20/100) × $150 = $30

Final Price = $150 - $30 = $120

Result: The item will cost $120 after the 20% discount.

Why This Calculation Matters

Practical Applications

Calculating discounts and sale prices
Determining tips at restaurants
Computing sales tax on purchases
Analyzing financial growth or decline
Understanding statistical data

Key Benefits

Make informed purchasing decisions
Compare values proportionally
Track changes over time
Budget more effectively
Understand relative sizes of quantities

Common Mistakes & Tips

A common mistake is to add the percentage increase directly to the original value. For example, a 20% increase on $100 is not $120, but rather $100 + (20% of $100) = $120. Always calculate the percentage amount first, then add or subtract it from the original value.

When calculating what percentage one number is of another, make sure you're dividing the smaller number by the larger one (unless you specifically want a percentage over 100%). For example, 25 is what percent of 200? The calculation is (25/200) × 100 = 12.5%, not (200/25) × 100 = 800%.

A 50% decrease followed by a 50% increase does not return you to the original value. For example, a $100 item decreased by 50% becomes $50. If that $50 item is then increased by 50%, it becomes $75, not $100. This is because the base value changes after the first calculation.

Frequently Asked Questions

For simple percentages, you can use mental math tricks. For 10%, just move the decimal point one place to the left. For 5%, calculate 10% and then halve it. For 25%, divide by 4. For 50%, divide by 2. For more complex percentages, break them down into simpler components (e.g., 17% = 10% + 5% + 2%).

Percentage change measures the difference between two values relative to the original value (old value). It's directional, showing increase or decrease. Percentage difference measures the difference between two values relative to their average, without regard to which is larger or smaller. It's always a positive value.

For compound percentage changes, you need to apply each percentage change sequentially to the result of the previous change. For example, for a 10% increase followed by a 5% increase on $100: First calculate $100 × 1.10 = $110, then calculate $110 × 1.05 = $115.50. The total compound increase is 15.5%, not simply 10% + 5% = 15%.

References & Disclaimer

Mathematical Disclaimer

This percentage calculator provides results for mathematical calculations only. While we strive for accuracy, rounding may occur based on the decimal places selected. For critical financial, scientific, or academic calculations, please verify results independently and consult with appropriate professionals.

References

Math Is Fun: Percentage - Comprehensive guide to percentage calculations and concepts
Khan Academy: Finding Percentages - Video tutorials on percentage calculations
Investopedia: Percentage Change - Financial applications of percentage calculations

Accuracy Notice

This calculator performs calculations to the precision selected by the user. Results may be rounded and should not be considered exact for applications requiring high precision. For financial decisions, always verify calculations with your financial institution or advisor.

About the Author

Kumaravel Madhavan

Web developer and data researcher creating accurate, easy-to-use calculators across health, finance, education, and construction and more. Works with subject-matter experts to ensure formulas meet trusted standards like WHO, NIH, and ISO.

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