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Percentage Calculator.
Calculate percentages, increases, decreases, and percentage changes
Set your values
Results update as you type.
How to Use
Basic: Calculate X% of Y
Of: Find what percentage X is of Y
Change: Calculate percentage change from X to Y
Increase/Decrease: Increase or decrease X by Y%
FAQs
How do I calculate what percentage A is of B?
Divide A by B and multiply by 100: (A ÷ B) × 100 = Percentage.
How do I calculate percentage increase or decrease?
Subtract the old value from the new value, divide by the old value, and multiply by 100.
How to Use the Percentage Calculator
Calculate percentages, percentage increases, decreases, and find what percentage one number is of another.
- Select the calculation type: Find percentage, Find percentage increase/decrease, or Find what percentage X is of Y.
- Enter the required values in the input fields.
- Click Calculate to see the result.
- The calculator will show both the numerical result and a breakdown of the calculation.
Percentage Formulas
Understanding the mathematical formulas behind percentage calculations helps you verify results and understand the math.
Find Percentage
To find what percentage a part is of a whole, divide the part by the whole and multiply by 100.
Example:
Input: Part = 25, Whole = 100
Calculation: (25 / 100) × 100
Result: 25%
Percentage Increase
Calculates the percentage increase from an original value to a new value.
Example:
Input: Original = 50, New = 75
Calculation: [(75 - 50) / 50] × 100
Result: 50% increase
Percentage Decrease
Calculates the percentage decrease from an original value to a new value.
Example:
Input: Original = 100, New = 80
Calculation: [(100 - 80) / 100] × 100
Result: 20% decrease
Find Value from Percentage
Finds the actual value when you know the percentage and the whole amount.
Example:
Input: Percentage = 15%, Whole = 200
Calculation: (15 / 100) × 200
Result: 30
Real-World Use Cases
Percentage calculations are used in countless everyday situations.
Discount Calculations
Calculate sale prices and discounts when shopping. Find the final price after a percentage discount.
Example: A $100 item with a 25% discount: $100 × 0.25 = $25 discount, final price = $75
Salary Raises
Calculate percentage increases in salary, or determine what percentage raise you received.
Example: Salary increased from $50,000 to $55,000: [(55,000 - 50,000) / 50,000] × 100 = 10% increase
Grade Calculations
Calculate test scores as percentages or determine what grade you need to achieve a target.
Example: Scored 85 out of 100: (85 / 100) × 100 = 85%
Tax Calculations
Calculate sales tax, income tax, or VAT using percentage rates.
Example: Purchase of $200 with 8% sales tax: $200 × 0.08 = $16 tax, total = $216
Investment Returns
Calculate return on investment or percentage gains/losses on investments.
Example: Investment grew from $1,000 to $1,200: [(1,200 - 1,000) / 1,000] × 100 = 20% return
Tips & Best Practices
Tips
- Always verify your percentage calculations by checking if the result makes sense relative to the original value.
- When calculating percentage change, remember that increases and decreases use different formulas.
- For percentage discounts, subtract the discount percentage from 100% first, then multiply by the original price.
- Round percentages appropriately based on the context - financial calculations often use 2 decimal places.
- Double-check your work by calculating the reverse: if you found 20% of 100 = 20, verify that 20 is 20% of 100.
Common Mistakes to Avoid
- Confusing percentage increase and decrease formulas - always subtract the smaller value from the larger.
- Forgetting to multiply by 100 when converting a decimal to a percentage.
- Using the wrong base value in percentage change calculations - always use the original value as the base.
- Mixing up part and whole when calculating what percentage one number is of another.
Related Resources
Related Calculators
Cite this calculator
Canonical URL: https://mathify.one/en/math/percentage
Cite as: Mathify. (2026). Percentage Calculator. https://mathify.one/en/math/percentage
Use Cases
Everyday Shopping Discounts
Quickly determine sale prices or savings when a discount percentage is applied to an item's original price.
Example: A $50 item with 25% off costs $37.50.
Financial and Business Analysis
Calculate percentage increases or decreases in revenue, expenses, or other metrics to assess performance.
Example: Sales rose from $10,000 to $12,500, a 25% increase.
Frequently Asked Questions
- How do I calculate a percentage of a number?
- Enter the percentage and the number. The calculator multiplies the number by the percentage (divided by 100) to give you the result. For example, 20% of 150 is 30.
- How do I calculate percentage increase or decrease?
- Input the original value and the new value. The calculator computes the difference, divides by the original, and multiplies by 100 to show the percentage change. A positive result indicates an increase, negative a decrease.
- Can this calculator find the percentage change between two numbers?
- Yes, it calculates the percentage change by comparing the difference to the original number. This is useful for tracking growth, price changes, or performance over time.
Tips & Common Mistakes
Tips
- Double-check that you enter the percentage as a number (e.g., 25) not a decimal (0.25) unless you intend to use decimal form.
- For percentage change, ensure you input the original value as the base, not the new value, to get the correct direction.
- Use the calculator to verify manual calculations, especially when dealing with large numbers or multiple steps.
- Remember that a percentage decrease is represented as a negative change; interpret the sign accordingly.
Common Mistakes to Avoid
- Confusing percentage points with percentage change: a rise from 10% to 15% is a 50% increase, not 5%.
- Entering the new value as the original when calculating percentage change, leading to an inverted result.
- Forgetting to convert a percentage to a decimal when doing manual calculations, but this calculator handles it for you.
Last updated: August 13, 2026