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.
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
6 Essential Percentage Formulas
Master these 6 formulas to handle almost any percentage scenario.
Formula 1: Find a Percentage of a Number
Result = Total × (Percentage ÷ 100)
Example: 15% of $200 = 200 × 0.15 = $30. Use for tips, discounts, commissions, and tax calculations.
Formula 2: Find What % One Number Is of Another
Percentage = (Part ÷ Whole) × 100
Example: 45 out of 60 students passed: 45 ÷ 60 × 100 = 75%. Use for test scores, completion rates, market share.
Formula 3: Find the Total When You Know the Percentage
Total = Part ÷ (Percentage ÷ 100)
Example: You paid $34 for a jacket that was 15% off. Original price: $34 ÷ 0.85 = $40.
Formula 4: Calculate Percentage Increase
% Increase = ((New - Original) ÷ Original) × 100
Example: Stock goes from $50 to $65: (65 - 50) ÷ 50 × 100 = 30% increase.
Formula 5: Calculate Percentage Decrease
% Decrease = ((Original - New) ÷ Original) × 100
Example: Price drops from $80 to $60: (80 - 60) ÷ 80 × 100 = 25% decrease.
Formula 6: Percentage Difference
% Difference = (|Value 1 - Value 2| ÷ Average of Both) × 100
Example: One product costs $100, another $120. Difference = 20 ÷ 110 × 100 = 18.2%.
Real-World Business Applications
Sales Growth
Revenue grew from $500K to $625K = 25% increase.
Market Share
Your $2M sales out of $10M market = 20% share.
Profit Margin
Gross Margin = (Revenue - COGS) ÷ Revenue × 100.
Conversion Rate
Visitors to buyers: 50 out of 1000 = 5% conversion rate.
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.
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.
Common Percentage Mistakes
Confusing Percentage Points with Percent Change
A rate rise from 5% to 8% is 3 percentage points, but a 60% increase in the rate. Know the difference for accurate reporting.
Wrong Direction in Increase/Decrease
Always divide by the original value, not the new value.
Adding Percentages Directly
A 20% discount followed by 10% off is 28% off, not 30%. The second discount applies to the already-reduced price.
Key Takeaways
- 6 formulas cover almost every percentage scenario you'll encounter
- Always divide by the original value when calculating percent change
- Percentage points ≠ percent change — know the difference for accurate reporting
Percentage Benchmarks by Context
Common percentage ranges to help you evaluate whether your numbers are typical.
| Context | Typical Range | Notes |
|---|---|---|
| Restaurant Tips (US) | 15%–20% | 18% is standard for good service |
| Sales Tax (US) | 0%–10% | Varies by state; average ~7% |
| Shopping Discounts | 10%–50% | Black Friday: 30%–70% off |
| Credit Card Interest | 15%–25% APR | Rewards cards often higher |
| Savings Account APY | 0.5%–5% | High-yield accounts: 4%–5% |
| Annual Stock Market Return | 7%–10% | S&P 500 long-term average |
| Markup (Retail) | 50%–100% | Clothing: 100%+; Groceries: 25%–50% |
| Student Loan Interest | 3%–7% | Federal loans typically lower |
| Mortgage Rates | 3%–8% | Depends on credit and market conditions |
| Subscription Churn Rate | 3%–8% monthly | SaaS: 3%–5% is healthy |
Key insight: A 20% discount during a sale is common, but a 20% tip is considered generous in many countries outside the US where tipping is not expected.
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 decrease?
Percentage Decrease = ((Original Value - New Value) ÷ Original Value) × 100. If a store price drops from $80 to $60: (80 - 60) ÷ 80 × 100 = 25% decrease.
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.
How do I calculate one number as a percentage of another?
Divide the part by the whole and multiply by 100. If 45 out of 60 students passed: 45 ÷ 60 × 100 = 75% passed.
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.
Percentage Calculator Pros & Cons
Pros
- Six calculation modes in one tool
- Instant results with step-by-step
- Quick preset buttons for common percentages
- Free forever — no subscriptions
- Works offline after page load
Cons
- No batch percentage calculation
- No dedicated mobile app
Reviewed by Shahid
Content Reviewer & Calculator SpecialistContent reviewer specializing in marketing, finance, health, and math calculators on GM Calculator.