Percentage Calculator | Free 6-Mode Percent Tool
Free percentage calculator with 6 modes. Find what is X% of Y, X is what % of Y, calculate percentage increase, decrease, difference, and more. Includes visual bars, quick presets, and formula explanations.
📖 Want to understand your results?
Read our complete guide to the Percentage Calculator — with real-world examples, expert insights, and pro tips.
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How to Calculate Percentage — Simple Formula
A percentage is a number or ratio expressed as a fraction of 100. The word comes from the Latin "per centum" meaning "by the hundred." The basic formula is:
The calculator above handles 6 different percentage scenarios. Here's how each one works:
❓ What is X% of Y?
Formula: (X ÷ 100) × Y
Example: What is 15% of 80? = (15 ÷ 100) × 80 = 12
📊 X is what % of Y?
Formula: (X ÷ Y) × 100
Example: 12 is what % of 80? = (12 ÷ 80) × 100 = 15%
🔄 X% of what is Y?
Formula: (Y ÷ X) × 100
Example: 15% of what is 12? = (12 ÷ 15) × 100 = 80
📈 % Increase / Decrease
Formula: ((New - Old) ÷ Old) × 100
Example: 100 → 150 = ((150-100) ÷ 100) × 100 = 50% increase
⚖️ % Difference
Formula: |A - B| ÷ ((A + B) ÷ 2) × 100
Example: 80 vs 100 = |80-100| ÷ 90 × 100 = 22.2% difference
➕ Add / Subtract %
Formula: X ± (Y% of X)
Example: 100 + 10% = 100 + 10 = 110 | 100 - 10% = 90
Common Percentage Calculations in Daily Life
🍽️ Restaurant Tips
15% of $80 = $12 tip. Use the "What is X% of Y?" mode with 15% and your bill amount.
🛍️ Shopping Discounts
25% off $200 = $50 savings. Use the "Subtract %" mode or "What is X% of Y?" to find the discount amount.
📈 Investment Returns
$1,000 → $1,200 = 20% return. Use "% Increase / Decrease" mode to calculate investment performance.
💰 Sales Tax
Add 8% tax to $50 = $54 total. Use "Add / Subtract %" mode for tax calculations.
📚 Grade Calculations
85 out of 100 = 85%. Use "X is what % of Y?" for test scores and grade calculations.
📊 Data Analysis
Compare two values with "% Difference" mode. Sales went from 500 to 750 units — a 40% increase.
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Percentage vs Percentage Points: What's the Difference?
A common confusion is the difference between percentage and percentage points. If a tax rate increases from 5% to 8%, that's a 3 percentage point increase, but a 60% increase in the tax rate.
Percentage Point Change
The absolute difference between two percentages. 8% - 5% = 3 percentage points. This does not use division.
Percent Change
The relative change. (8% - 5%) ÷ 5% × 100 = 60% increase. Use the "% Increase / Decrease" mode above.
Reviewed by Emily Watson, M.Ed.
Mathematics EducatorMathematics teacher and curriculum designer with 15+ years of experience.
Percentage Calculator Pros & Cons
Pros
- ✅ Six calculation modes in one tool
- ✅ Instant results with step-by-step
- ✅ Quick preset buttons for common %s
- ✅ Free forever — no subscriptions
- ✅ Works offline after page load
Cons
- ✗ No batch percentage calculation
- ✗ No dedicated mobile app
Frequently Asked Questions
How do I calculate a percentage of a number?
To find X% of Y, use the formula (X ÷ 100) × Y. For example, to find 15% of 80: (15 ÷ 100) × 80 = 12. Use the 'What is X% of Y?' mode in our calculator for instant results.
What is the percentage formula?
The basic percentage formula is: Percentage = (Value ÷ Total) × 100. For percentage change: ((New - Old) ÷ Old) × 100. For percentage difference: |A - B| ÷ ((A + B) ÷ 2) × 100.
How do I calculate percentage increase?
Subtract the original value from the new value, divide by the original value, then multiply by 100. For example: ((150 - 100) ÷ 100) × 100 = 50% increase. Use our '% Increase / Decrease' mode.
How do I calculate percentage difference between two numbers?
The percentage difference is calculated as: |A - B| ÷ ((A + B) ÷ 2) × 100. For example, between 80 and 100: |80-100| ÷ 90 × 100 = 22.2% difference. Use our '% Difference' mode.
What is a reverse percentage?
A reverse percentage finds the original value when you know the percentage and the result. The formula is: (Result ÷ Percentage) × 100. For example, if 15% of a number is 12, the original number is (12 ÷ 15) × 100 = 80.
How do I convert a fraction to a percentage?
Divide the numerator by the denominator, then multiply by 100. For example, 3/4 = 3 ÷ 4 = 0.75 × 100 = 75%. See our quick reference table for common fraction-to-percentage conversions.
How do I calculate a 20% tip?
To calculate a 20% tip on a bill, use the formula: (20 ÷ 100) × Bill Amount. For an $80 bill: 0.20 × $80 = $16 tip. Use our 'What is X% of Y?' mode with 20% and your bill amount.
What is the difference between percentage and percentage points?
Percentage points measure the absolute difference between two percentages (e.g., 8% - 5% = 3 percentage points). Percent change measures the relative difference: ((8-5) ÷ 5) × 100 = 60% increase.
How do I calculate percentage off a price?
To calculate a discount: multiply the original price by the discount percentage (as a decimal), then subtract. For 25% off $200: 200 × 0.25 = $50 discount. Sale price = $200 - $50 = $150. Or use our 'Add / Subtract %' mode.
What is 10% of 100?
10% of 100 is 10. The calculation is (10 ÷ 100) × 100 = 10. You can use our quick preset buttons (10%, 15%, 20%, 25%, 50%) for common percentage calculations.
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