Percentage Calculator

How to use it

1. Pick the calculator that matches your question.
2. Type the two numbers into the boxes.
3. Read the answer below, which updates instantly as you type.

What is a percentage?

A percentage is a share of 100, so 25% means 25 out of every 100, whatever the whole happens to be. Every proportion problem on this page comes back to one core formula: part = percent ÷ 100 × whole. To find 15% of 200, divide 15 by 100 to get 0.15, then multiply by 200 to get 30.

part = percent ÷ 100 × whole

The other two calculators rearrange the same math. To learn what percent a part is of a whole, divide the part by the whole and multiply by 100. To measure percent change, divide the difference by the starting value and multiply by 100. Those three moves cover tips, tax, discounts, grades and raises.

Worked example

Fraction, decimal and percent equivalents

How to work out a percentage

A percent is a fraction of 100, so every percentage problem comes down to one of three moves. To find a percent of a number, divide the percent by 100 and multiply: 15% of 200 is 0.15 × 200, which is 30. That single formula covers tips, sales tax, commissions and discounts. An 18% tip on a $64.50 check is 0.18 × 64.50, or $11.61.

To find what percent one number is of another, divide the part by the whole and multiply by 100. A test score of 42 out of 60 is 42 ÷ 60 × 100, which is 70%. Percent change compares a starting value with an ending value: subtract the old from the new, divide by the old, and multiply by 100. Going from 80 to 100 is a 25% increase, because the difference of 20 is a quarter of the starting 80.

Discounts, markups and reverse percentages

Taking a percentage off is easier if you multiply by what is left. A 20% discount leaves 80% of the price, so $50 becomes 50 × 0.80, or $40. Adding a percentage works the same way in reverse: 8.25% sales tax on a $40 item gives 40 × 1.0825, or $43.30. Reverse percentages catch people out. If a jacket costs $60 after a 25% markdown, the original price is 60 ÷ 0.75, which is $80, not $60 plus 25%.

Percent change is not symmetric. A rise from 80 to 100 is 25%, but the fall from 100 back to 80 is only 20%, because the second change is measured against the larger starting number. The same trap shows up with a 50% loss followed by a 50% gain: $100 drops to $50, then climbs back only to $75. The third calculator uses the starting value as the base every time, which is the convention in finance, statistics and news reports.

Common uses

• Calculating tips, sales tax and discounts
• Turning test scores into percentages
• Measuring price increases and pay raises
• Working out commissions and interest
• Finding the original price before a markdown
• Comparing growth between two periods

When to use it

• You want to know how to calculate a 20 percent tip on a restaurant check without opening a spreadsheet.
• You scored 42 out of 60 on a test and need to know what percent 42 is of 60 (it is 70%).
• A price moved from $80 to $100 and you want the percent increase between two numbers.
• You are checking how to find the original price before a discount when only the sale price is on the tag.
• You need the percent difference between last month's sales and this month's for a report.

Related tools

Use the Average Calculator when you need the mean, median or mode of a whole list rather than a single percent.

The Grade Calculator turns percent scores and their weights into a class grade and tells you what you need on the final.

The Sum Calculator adds a long list of numbers first, which helps before you turn a total into a percent.