Percentage of a number
Tips, discounts, commissions.
What is of ?
20 ÷ 100 × 150 = 30
What percent
Test scores, shares of a budget, survey results.
is what percent of ?
30 ÷ 150 × 100 = 20%
Percentage change
Price rises, growth and drops between two values.
From to
(180 − 150) ÷ 150 × 100 = +20%
Add or subtract a percentage
Markups, raises, discounts.
What is ?
150 × (1 + 20 ÷ 100) = 180
Original value
The number before a percentage was added or taken off.
is than what?
120 ÷ (1 + 20 ÷ 100) = 100
Everything is calculated in your browser, and your last numbers are saved there for next time. Nothing is sent to Tooly's server.
Embed this tool on your site
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About the Percentage Calculator
Five small calculators answer the percentage questions that come up every day: what is 20% of 150, what percent 30 is of 150, how much a value rose or fell from one number to another, what a number is plus or minus a percentage, and what the original value was before a percentage was added or taken off. Results update as you type and show the formula behind them.
How to use the Percentage Calculator
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Find the question you need
Each card is a sentence with the numbers in boxes, such as What is [20]% of [150]? Pick the one that matches your question; the example numbers show how it works.
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Type your numbers
The answer updates as you type. Use a point or a comma for decimals. If a box holds something that is not a number, or the answer would need a division by zero, the card shows — and says why. On the add-or-subtract and original-value cards, switch between plus and minus (or more and less).
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Check the formula and copy
The line under each result shows the calculation, such as 20 ÷ 100 × 150 = 30. Copy puts the number on the clipboard without thousands separators, ready to paste into a spreadsheet or a message.
When to use it
Discounts and sale prices
Work out a price with 25% off on the add-or-subtract card, or find the price before a discount with the original-value card.
Grades, budgets and statistics
See what share of a total a score, an expense or a group is: 42 out of 60 is 70%.
Growth and price changes
Compare two figures, such as last month's and this month's sales, and get the percentage increase or decrease with its sign.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100: 20% of 150 is 150 × 20 ÷ 100 = 30. It works the same with decimals: 12.5% of 80 is 10.
How is percentage change calculated?
Subtract the starting value from the final one, divide by the starting value and multiply by 100: from 150 to 180 is (180 − 150) ÷ 150 × 100 = +20%. A change from 0 has no percentage, because any change would be infinite. With a negative starting value the calculator divides by its absolute value, so going from −50 to −25 counts as a 50% increase.
Why does adding 20% and then taking 20% off not give back the same number?
Because each percentage is taken of a different number. 100 plus 20% is 120, but 20% of 120 is 24, so 120 minus 20% is 96. To undo a 20% increase, divide by 1.2 instead: that is what the original-value card does (120 ÷ 1.2 = 100).
How do I find the original value before a percentage was added?
Divide by 1 plus the percentage as a decimal: a price of 121 that includes 21% tax was 121 ÷ 1.21 = 100 before tax. For a value after a discount, divide by 1 minus the percentage: 80 after 20% off was 80 ÷ 0.8 = 100. Taking off 100% leaves 0 whatever the original was, so it cannot be worked back.
Can I type decimals with a comma?
Yes: 12.5 and 12,5 both mean twelve and a half. With both separators, the last one marks the decimals (1,234.5). On this English page a comma followed by exactly three digits, as in 1,500, is read as a thousands separator. Results show up to four decimals, but the calculation uses full precision.
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