Percentage Calculator
Calculate percentages: find X% of Y, what percent X is of Y, or the percentage change between two values.
Percentage calculator
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Examples
How It Works
There are three common percentage problems. Finding X% of Y means multiplying: convert the percentage to a decimal (divide by 100) and multiply by the value. Finding what percent X is of Y means dividing: divide the part by the whole and multiply by 100. Percentage change measures how much a value has increased or decreased: subtract the old value from the new, divide by the old value, and multiply by 100.
Percentages appear everywhere in daily life: store discounts and sales tax, restaurant tips, exam grades, interest rates on loans and savings, nutritional labels, battery levels, and statistical data. Understanding these three formulas covers virtually every percentage calculation you will encounter.
Tips & Best Practices
Frequently Asked Questions
What is a percentage?
A percentage is a way of expressing a number as a fraction of 100. The word comes from Latin "per centum" meaning "by the hundred." For example, 45% means 45 out of 100.
How do I calculate percentage increase or decrease?
Percentage change = ((New Value - Old Value) / Old Value) × 100. A positive result means an increase, and a negative result means a decrease. For example, going from 80 to 100 is a 25% increase.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, to find what percent 30 is of 200: (30 / 200) × 100 = 15%. This works for any pair of numbers.
What is the difference between percentage points and percent?
Percentage points measure the arithmetic difference between two percentages, while percent measures the relative change. Going from 10% to 15% is a 5 percentage point increase but a 50% relative increase.
How do I calculate a percentage in my head?
Break the percentage into easy parts. To find 15% of a number, calculate 10% (move the decimal one place left) and add half of that for the remaining 5%. For example, 15% of 80: 10% is 8, 5% is 4, so 15% is 12. You can also use the commutative trick: 8% of 50 equals 50% of 8, which is 4.
What is the difference between percentage and percentile?
A percentage represents a portion of a whole (e.g., you scored 85% on a test). A percentile indicates your rank relative to others (e.g., you are in the 90th percentile means you scored higher than 90% of test-takers). Percentiles are used in standardized testing, growth charts, and statistical analysis.
How do I calculate percentage increase and decrease?
For an increase: Percentage Increase = ((New Value − Old Value) / Old Value) × 100. For a decrease: Percentage Decrease = ((Old Value − New Value) / Old Value) × 100. Note that a 50% increase followed by a 50% decrease does not return to the original — it leaves you at 75% of the starting value.
What does 'basis points' mean?
A basis point is one hundredth of a percentage point, or 0.01%. It is commonly used in finance to describe small changes in interest rates or yields. For example, a rate increase from 3.50% to 3.75% is a 25 basis point increase. 100 basis points equals 1 percentage point.
How do compound percentages work?
Compound percentages apply a percentage change repeatedly over time, with each period's change applied to the updated value. For example, $100 growing at 10% per year becomes $110 after year one, then $121 after year two (10% of 110), not $120. The formula is Final = Initial × (1 + rate)^periods. Compounding is the basis of savings growth, loan interest, and inflation.
Why is X% of Y equal to Y% of X?
Because multiplication is commutative: X% of Y = (X/100) × Y = (Y/100) × X = Y% of X. This trick is useful for mental math — 8% of 50 is the same as 50% of 8, which is obviously 4. Whenever one of the numbers is easier to work with, swap them.