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- A percentage is a number out of 100, so 15% means 15 out of every 100, or 0.15 as a decimal.
- This calculator handles four jobs: a percent of a number, what percent one number is of another, percentage change, and increasing or decreasing a number by a percent.
- To find X% of Y, multiply Y by X and divide by 100. Fifteen percent of 200 is 30.
- Percentage change is not symmetric: 80 to 100 is a 25% rise, but 100 back to 80 is a 20% fall.
How to use the percentage calculator
Pick what you want to find
Choose X% of Y, X is what % of Y, percentage change, or increase or decrease by a percent from the first list.
Enter your numbers
The boxes change to match your choice. You do not need to type percent signs or currency symbols.
Read the answer
The result appears straight away, with the formula written next to it.
Follow the steps
The Step by step panel shows each calculation, so you can check it or copy it into your homework.
The percentage formulas
The word percent means per hundred. So 15% is 15 per hundred, which is the fraction 15/100 or the decimal 0.15. Every percentage problem is that conversion followed by a multiplication or a division.
Four percentage formulas
X% of Y = (X ÷ 100) × Y
X is what % of Y = (X ÷ Y) × 100
Percentage change = ((New − Old) ÷ |Old|) × 100
Increase or decrease: New = Y × (1 ± X ÷ 100)
In the change formula, |Old| means the starting value with any minus sign removed.
Worked examples
Example 1: a percent of a number
What is 15% of 200?
So 15% of 200 is 30.
Example 2: what percent is this?
A student scores 45 out of 60. What percent is that?
The student scored 75%.
Example 3: percentage change
A jacket drops in price from $250 to $200.
The negative sign tells you the price went down.
Example 4: a price with sales tax
An item costs $59.99 and sales tax is 8.25%.
Round money to two decimals only at the very end.
Why percentage change is not symmetric
A 25% rise from 80 gives 100, but a fall back from 100 to 80 is only 20%, because the second percentage is measured against a bigger starting number. The same trap appears with prices: a 50% rise followed by a 50% fall leaves you 25% below where you began (100 becomes 150, then 75). Always ask which number the percentage is measured against.
Common percentages
Handy conversions
Percent, decimal and fraction forms side by side.
To find 10% of any number, move the decimal point one place to the left.
Where a percentage calculator helps
Shopping and discounts
Work out sale prices, sales tax and tips before you pay.
Business and pricing
Measure margins, markups and month-on-month growth in sales.
School and exams
Turn scores into percentages and check each step of your homework.
Money and savings
See how a change in a rate affects your savings, prices or bills.
Need the average of several percentages? Use the average calculator. To find the side of a square from its area, try the square root calculator, and to count the days between two dates use the date difference calculator.
Percentage calculator FAQ
How do I calculate a percentage of a number?
Divide the percent by 100 and multiply by the number. For 15% of 200, 15 ÷ 100 = 0.15 and 0.15 × 200 = 30.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For 45 out of 60, 45 ÷ 60 × 100 = 75%.
How is percentage change calculated?
Subtract the old value from the new value, divide by the old value, then multiply by 100. A positive result is an increase and a negative result is a decrease.
What is the difference between a percentage and percentage points?
A rise from 10% to 12% is 2 percentage points, but it is a 20% increase in the rate itself, because 2 ÷ 10 = 0.2.
How do I add or take off a percentage?
Multiply by 1 plus the percent for an increase, or by 1 minus the percent for a decrease. To add 15% multiply by 1.15, and to take off 15% multiply by 0.85.
Can a percentage be more than 100?
Yes. It happens when the new value is more than double the old one, such as growth from 20 to 150, which is a 650% rise. A decrease, however, cannot go beyond 100% when the numbers are positive.
Related calculators
Need the smallest number that several numbers all divide into? Try the LCM calculator, which shows the least common multiple with steps.