How to Calculate Percentage: Formula, Examples & Calculator
Learn how to calculate percentage with our complete guide. Includes formula, percentage increase/decrease examples and free calculator.
Basic Percentage Formula
A percentage represents a fraction of 100. The basic formula to calculate percentage is:
Percentage = (Part ÷ Whole) × 100
Example: What is 25% of 80?
Step 1: Convert 25% to decimal → 25 ÷ 100 = 0.25
Step 2: Multiply by the whole → 0.25 × 80 = 20
Answer: 25% of 80 is 20
How to Calculate Percentage Increase
To find the percentage increase from an old value to a new value, use this formula:
% Increase = ((New Value - Old Value) ÷ Old Value) × 100
Example: Price Increase
A product price changed from $50 to $65. What is the percentage increase?
Step 1: Calculate the difference → $65 - $50 = $15
Step 2: Divide by original value → $15 ÷ $50 = 0.30
Step 3: Convert to percentage → 0.30 × 100 = 30%
Answer: The price increased by 30%
How to Calculate Percentage Decrease
The formula for percentage decrease is similar to increase:
% Decrease = ((Old Value - New Value) ÷ Old Value) × 100
Example: Discount
An item originally priced at $80 is now on sale for $60. What is the discount percentage?
Step 1: Calculate the difference → $80 - $60 = $20
Step 2: Divide by original value → $20 ÷ $80 = 0.25
Step 3: Convert to percentage → 0.25 × 100 = 25%
Answer: The discount is 25%
Reverse Percentage Calculation
Sometimes you need to find the original value before a percentage change was applied:
Original Value = New Value ÷ (1 ± Percentage)
Example: Finding Original Price After Discount
After a 20% discount, an item costs $80. What was the original price?
Step 1: Formula: Original = $80 ÷ (1 - 0.20) = $80 ÷ 0.80 = $100
Answer: The original price was $100
Real-World Percentage Calculations
🏦 Banking & Finance
Calculate interest rates, loan percentages, and investment returns using the same formulas above.
🛒 Shopping & Sales
Determine actual savings during sales, compare discount percentages, and calculate final prices.
📊 Data & Statistics
Express proportions as percentages, calculate growth rates, and analyze changes over time.
📚 Academics & Education
Calculate grades, test scores, and academic performance using percentage calculations.
Try Our Free Percentage Calculator
Skip the manual calculations! Use our free percentage calculator for instant, accurate results.
Percentage →Frequently Asked Questions
How do I calculate 10% of a number?
To calculate 10% of any number, simply divide by 10 or move the decimal point one place to the left. For example, 10% of 150 = 150 ÷ 10 = 15.
What is the easiest way to calculate percentages mentally?
Break percentages into simpler parts: 50% = divide by 2, 25% = divide by 4, 10% = divide by 10, 1% = divide by 100. Then combine as needed.
How do I calculate percentage increase in Excel?
Use the formula: =(New-Old)/Old. Format the result as a percentage by pressing Ctrl+Shift+% in Excel or selecting percentage format.
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About the Author
Written by PercentHub Team
Expert team specializing in financial and health calculations
⚠️Disclaimer
The results from our calculators are for informational purposes only. While we strive for accuracy, we cannot guarantee the completeness or reliability of the information.