Percentage calculator.
Find percentages, percentage change, and what percent one number is of another..
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About the percentage calculator
A percentage expresses a number as a fraction of 100. For example, 25% means 25 out of 100, or 0.25 as a decimal. Percentages are useful because they make it easy to compare values of different sizes, such as discounts, test scores, tax rates, price changes, interest rates, profit margins, and growth.
This calculator handles the most common percentage problems: finding a percentage of a number, finding what percent one number is of another, finding the original number, increasing or decreasing a value by a percentage, calculating percentage change, and comparing two numbers by percentage difference.
Common percentage calculations
What is A% of B?
Use this when you need a portion of a number, such as a discount, tax, or tip.
Formula: (A ÷ 100) × B
Example: 15% of 200 = 30
A is what percent of B?
Use this to compare a part with a whole, such as a score out of total points.
Formula: (A ÷ B) × 100
Example: 30 is 15% of 200
A is B% of what number?
Use this when you know the part and the percentage but need the original whole.
Formula: A ÷ (B ÷ 100)
Example: 30 is 15% of 200
Percentage increase or decrease
Use this for price changes, raises, markdowns, or growth and decline.
Increase: A × (1 + B ÷ 100)
Decrease: A × (1 - B ÷ 100)
Percentage change
Use this when comparing an old value with a new value.
Formula: ((New - Old) ÷ Old) × 100
Example: 200 to 230 = 15% increase
Percentage difference
Use this to compare two values without treating either number as the original.
Formula: |A - B| ÷ ((A + B) ÷ 2) × 100
Example: 10 and 6 = 50% difference
Percentage formula table
| Calculation | Formula | Example |
|---|---|---|
| A% of B | (A ÷ 100) × B | 20% of 50 = 10 |
| A is what % of B | (A ÷ B) × 100 | 10 is 20% of 50 |
| A is B% of what | A ÷ (B ÷ 100) | 10 is 20% of 50 |
| Increase A by B% | A × (1 + B ÷ 100) | 50 + 20% = 60 |
| Decrease A by B% | A × (1 - B ÷ 100) | 50 - 20% = 40 |
| Percentage change | ((New - Old) ÷ Old) × 100 | 50 to 60 = 20% |
| Percentage difference | |A - B| ÷ average(A,B) × 100 | 10 and 6 = 50% |
Where percentages are used
Percentages are used in discounts, sales tax, tips, loan interest, investment returns, salary raises, exam scores, profit margins, inflation, and price changes.
A $80 item with 25% off saves $20 and costs $60.
A 20% tip on a $45 bill is $9.
A $50,000 salary increased by 6% becomes $53,000.
A price moving from $120 to $150 is a 25% increase.
FAQ
What is the easiest way to calculate a percentage?
Convert the percentage to a decimal by dividing it by 100, then multiply by the number. For example, 20% of 50 is 0.20 × 50 = 10.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100. For example, a price increasing from 50 to 60 is ((60 - 50) ÷ 50) × 100 = 20%.
How do I calculate percentage decrease?
Subtract the new value from the old value, divide by the old value, then multiply by 100. For example, a price falling from 60 to 45 is ((60 - 45) ÷ 60) × 100 = 25% decrease.
What is the difference between percentage change and percentage difference?
Percentage change compares a new value with an original value, so direction matters. Percentage difference compares two values using their average as the base, so it is useful when neither value is the starting point.
How do I calculate a discount percentage?
Multiply the original price by the discount percent divided by 100. Subtract that discount from the original price to get the sale price.
Why can percentage increase and decrease give different results?
Percentages depend on the base value. A 50% increase from 100 gives 150, but a 50% decrease from 150 gives 75 because the second calculation uses 150 as the base.