How to Calculate Percentages: 6 Formulas You'll Use Every Day

Master percentage calculations for business and everyday life. Learn the 6 essential formulas — basic percentage, percent increase/decrease, percentage of a total, and percentage difference — with real examples.

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The Basic Percentage Formula

Percentage = (Part ÷ Whole) × 100. A percentage is a fraction of 100 — "per cent" literally means "per hundred."

Formula 1: Find a Percentage of a Number

Result = Total × (Percentage ÷ 100). Example: 15% of $200 = 200 × 0.15 = $30. Use this 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 this for test scores, completion rates, and 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. The 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.

Common 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
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%

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

Ready to calculate? Use our Percentage Calculator for instant results.

FAQs

How do I calculate a percentage of a number?

Multiply the number by the percentage (as a decimal). For 15% of 200: 200 × 0.15 = 30. The formula is: Percentage × Total ÷ 100.

How do I calculate percentage increase?

Percentage Increase = ((New Value - Original Value) ÷ Original Value) × 100. If a stock goes from $50 to $65: (65 - 50) ÷ 50 × 100 = 30% increase.

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 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 the difference between percentage increase and percentage point increase?

Percentage increase is relative to the original value. Percentage points are absolute differences. If a tax rate rises from 5% to 8%, it's a 3 percentage point increase but a 60% increase in the rate.