Percentage Calculator

This percentage calculator works out the answer as you type: enter two numbers into any row. Each row answers one of the six questions people ask most often when working out a percentage, from a percentage of a number through percentage change to a percentage off a price. The row you are working in shows the calculation with your numbers plugged in, so you can check the result or copy the working into homework, a report, a spreadsheet or an email.

Working out percentages: six questions, one page

• What is 20 % of 150? This is the basic percentage formula: multiply the value by the percentage and divide by 100: 150 × 20 / 100 = 30.
• 30 is what percent of 150? Divide the part by the whole and multiply by 100: 30 / 150 × 100 = 20 %.
• Percentage change between two numbers, like 80 and 100. Take the difference, divide it by the starting value: (100 − 80) / 80 × 100 = +25 %. Going back from 100 to 80 is only −20 %, because the base is now bigger. The calculator shows both.
• Add or subtract a percentage. 150 + 20 % = 180, 150 − 20 % = 120. The +/− button switches between the two.
• 30 is 20 % of what? Work back to the whole: 30 / 20 × 100 = 150.
• From 12 % to 15 %. That is +3 percentage points, but a relative rise of 25 %. More on that below.

Under every row a small dimension line shows the proportion: how big the part is compared with the whole, or how far the value moved. The arrow keys change a number by 1 (with Shift by 10), and pasted values like “1,234.50 $” or “15 %” are cleaned up on their own.

Percent or percentage point?

When an interest rate goes from 5 % to 6 %, it went up by one percentage point, but by 20 percent relative to where it started. News reports mix the two up all the time, and the difference is big. On a loan, one point can mean hundreds a month, which is easy to see in the rent vs. mortgage calculator. The last row of the calculator gives you both numbers at once. Wikipedia has more examples.

Percentage change: why +10 % and then −10 % is not zero

A percentage increase of 10 % takes a price of 100 up to 110. A percentage decrease of 10 % is then taken from 110, which is 11, so the price ends at 99. Each change is calculated from the current value, not the original one. The Chained changes block shows this step by step for as many changes as you like: the running value after each step, the real total change and the change you would need to get back to the start.

Percentage discount, margin and markup

A discount is the most straightforward percentage off calculation: 25 % off 1,290 leaves 967.50 and saves you 322.50. The calculator also tells you that to get back to the original price later, the price would have to rise by 33.33 %, not 25 %.

Margin and markup confuse people more. If you buy something for 800 and sell it for 1,000, your profit is 200.

• Margin is the profit as a share of the selling price: 200 / 1,000 = 20 %.
• Markup is the profit as a share of the cost price: 200 / 800 = 25 %.

Same prices, two different percentages. The block draws both on one bar, so you can see which base each one is measured against.

Percentages of a total that add up to 100 %

Enter several amounts, for example what each person paid towards a shared bill, and the calculator shows what percentage of the total each one is, as a table and a bar. Rounding usually breaks the total: three equal amounts come out as 33 + 33 + 33 = 99 %. This calculator uses the largest remainder method, so the rounded shares always add up to exactly 100 %, and it tells you when plain rounding would have been off.

Frequently asked questions

How do I calculate a percentage of a number?

Multiply the number by the percentage and divide by 100. 15 % of 80 is 80 × 15 / 100 = 12. You can also move the decimal point: 15 % is 0.15, and 80 × 0.15 = 12. A percentage is one hundredth of a whole, which is why you divide by 100.

How do I calculate percentage change?

Subtract the old value from the new one, divide the result by the old value and multiply by 100. From 80 to 100: (100 − 80) / 80 × 100 = 25 %. A negative result means a decrease.

Why is a 20 % drop not undone by a 20 % rise?

Because the rise is calculated from a smaller number. 100 minus 20 % is 80, and 80 plus 20 % is only 96. To get from 80 back to 100 you need 25 %.

What is the difference between margin and markup?

Both describe the same profit. Margin divides it by the selling price, markup divides it by the cost price. Buying at 800 and selling at 1,000 gives a 20 % margin and a 25 % markup.

Can I use a comma as the decimal separator?

Yes. The calculator reads both 1.5 and 1,5, as well as numbers with thousands separators or a currency sign. Results are written in the format used by the language of the page.

Are my numbers sent anywhere?

No. Everything is calculated in your browser. The numbers are only kept in the page address, so you can bookmark a calculation or send the link to someone.

You can find more calculating tools in the Math category, such as the prime number generator or the Roman numeral converter.