A free percentage calculator that solves the three questions people actually ask: percent of a number, what percent one number is of another, and percent change between two values.
Pick a tab, type your numbers, and the answer appears as you go. Nothing to install, no sign up, and no limit on how often you use it. The math runs right inside your browser, so your figures never leave your device.
Below the calculator you will find the formulas written out in plain language, worked examples for each one, a conversion table of common percentages, and answers to the questions that come up most often. Whether you are checking a sale price, sorting out a tip, or tracking growth for work, the percentage calculator handles the arithmetic and the guide explains the reasoning.
Percentage Calculator
Free Percentage Calculator
Three quick percentage tools in one. Pick a tab and the answer updates as you type.
What is % of ?
30
is what percent of ?
15%
From to
25%
How to work out a percentage
Percent of a number. Divide the percent by 100, then multiply by the number. So 15 percent of 200 is 0.15 times 200, which is 30.
What percent one number is of another. Divide the first number by the second, then multiply by 100. So 30 out of 200 is 0.15 times 100, which is 15 percent.
Percent change. Subtract the old value from the new value, divide by the old value, then multiply by 100. Going from 200 to 250 is 50 divided by 200 times 100, which is a 25 percent increase.
The calculator above does the math for you, but knowing the formula lets you sanity check a result and work one out when no screen is handy. Percent means per hundred, so every percentage question boils down to comparing a part against a whole.
Percent of a number
Turn the percent into a decimal by dividing it by 100, then multiply. To find 15 percent of 200, change 15 into 0.15 and multiply by 200, which gives you 30. As a formula: the percent divided by 100, times the number.
What percent one number is of another
Divide the part by the whole, then multiply by 100. If 30 people out of 200 said yes, divide 30 by 200 to get 0.15, then multiply by 100 for 15 percent.
Percent change between two numbers
Subtract the old value from the new one, divide that gap by the old value, then multiply by 100. Moving from 200 to 250 leaves a gap of 50, and 50 divided by 200 is 0.25, so you have a 25 percent increase. A negative answer means the number went down.
Percentage Increase and Percentage Decrease
To add a percentage, multiply by 1 plus the decimal. A 20 percent raise on a 50,000 dollar salary is 50,000 times 1.20, which lands at 60,000. To take a percentage off, multiply by 1 minus the decimal. A 20 percent discount on a 60 dollar jacket is 60 times 0.80, or 48 dollars.
Here is the part that surprises almost everyone. A 20 percent drop followed by a 20 percent rise does not return you to where you began. Start at 100 and drop to 80. Now add 20 percent of 80, which is 16, and you finish at 96. The second percentage is measured against a smaller base, so it simply cannot carry the same weight.
That same logic explains why a discount cannot be undone by adding the identical percentage back. To reverse a 20 percent markdown, divide by 0.80 rather than multiplying by 1.20.
Percent Versus Percentage Points
If a rate climbs from 4 percent to 6 percent, that is a rise of 2 percentage points. It is also a 50 percent increase. Both statements are correct, and they describe very different things. Headlines blur the two constantly, usually in whichever direction sounds more dramatic, so it pays to check which one is meant before you react to the number.
Common Percentages at a Glance
Some fractions show up often enough that memorizing them saves real time.
Fraction
Decimal
Percent
1/10
0.1
10%
1/8
0.125
12.5%
1/5
0.2
20%
1/4
0.25
25%
1/3
0.333
33.3%
1/2
0.5
50%
2/3
0.667
66.7%
3/4
0.75
75%
Where a Percentage Calculator Comes in Handy
Percentages run quietly through most money decisions and plenty of daily ones too.
Shopping. Figuring the real price after a markdown, or checking whether a coupon beats a storewide sale.
Tips and splitting bills. Working out 18 or 20 percent, then dividing the total across the table.
Sales tax. Adding tax to a sticker price, or pulling tax back out of a total you already paid.
Grades and test scores. Turning points earned into a percentage, or finding what you need on the final exam.
Commission and raises. Checking a pay bump or a cut of a sale before you sign anything.
Business numbers. Growth rates, conversion rates, discount policy, and profit on a product line.
Budgets. Seeing what share of your take home pay each category is quietly eating.
Mistakes People Make With Percentages
Adding percentages that sit on different bases. Ten percent of one number plus ten percent of another does not equal 20 percent of anything.
Reversing a discount by adding the same percent back. As shown above, that always lands you short of the original price.
Mixing up markup and margin. A 50 percent markup is not a 50 percent margin. Our markup and margin calculator keeps the two straight.
Reading a percent with no raw number attached. A 300 percent jump might mean one case became four. Always ask what the starting count was.
Assuming coupons stack cleanly. Two 25 percent discounts applied one after the other give you about 44 percent off, not 50.
Frequently Asked Questions
How do I work out a percentage in my head?
Start with 10 percent, which just means moving the decimal one place left. Ten percent of 80 is 8. From there you can build almost anything. Twenty percent is double that, 5 percent is half of it, and 15 percent is 10 percent plus 5 percent.
What is the formula for percent change?
New value minus old value, divided by the old value, times 100. The old value always sits on the bottom, and that is where most errors creep in.
How do I remove sales tax from a total?
Divide rather than subtract. If the rate is 7 percent, divide the total by 1.07 to get the pre tax price. Subtracting 7 percent from the total gives a slightly wrong answer every time.
Can a percentage be more than 100?
Yes. Anything above 100 percent simply means the part is bigger than the whole you compared it to. Sales that triple are a 200 percent increase, since the growth is twice the original amount on top of what was already there.
Is this percentage calculator free to use?
Completely. No account, no email, and no limit on how many times you use it. Everything runs in your browser, so nothing you type gets sent anywhere.
How do I calculate a sale price?
Subtract the discount percent from 100, turn that into a decimal, then multiply by the original price. For 35 percent off a 120 dollar item, multiply 120 by 0.65 to get 78 dollars.
