Percentage Calculator
Work out X% of a number, what percent one number is of another, percent change, and the original number before a discount.
1. Pick a calculation and enter the numbers
Enter two numbers and the answer appears right away.
2. Result
Use the copy buttons to copy just the number.
- x% of it
- —
- Plus x%
- —
- Minus x%
- —
Decimal places (rounded)
Everything is calculated on this device. The numbers you enter are never sent anywhere.
Results that don't divide evenly are rounded to the decimal places you pick and shown with “≈”.
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How to use
1. Work out X% of a number
Under “Type of calculation”, tap “What is X% of Y?” and enter the “Number” and the “Percent”. The “Result” below shows “15% of it” right away, plus the number increased and decreased by 15%.
Under “Type of calculation” on the left, click “What is X% of Y?” and enter the “Number” and the “Percent”. The “Result” on the right shows “15% of it” right away, plus the number increased and decreased by 15%.
2. Find what percent one number is of another
Tap “X is what % of Y?” and enter the “Part” and the “Whole”. The “Result” below shows the “Percentage” and what is “Remaining”.
Click “X is what % of Y?” and enter the “Part” and the “Whole”. The “Result” on the right shows the “Percentage” and what is “Remaining”.
3. Find the percent change
Tap “Percent change” and enter the “Old value” and the “New value”. The “Result” below shows the change with “+” for an increase or “-” for a decrease, plus the difference and the ratio.
Click “Percent change” and enter the “Old value” and the “New value”. The “Result” on the right shows the change with “+” for an increase or “-” for a decrease, plus the difference and the ratio.
4. Work back to the original number
Tap “Find the original” and enter the “Known number” and the “Percent”. With 800 and 20, for example, “Before a 20% decrease” shows the price before a 20% discount brought it to 800 (1,000).
Click “Find the original” and enter the “Known number” and the “Percent”. With 800 and 20, for example, “Before a 20% decrease” shows the price before a 20% discount brought it to 800 (1,000).
5. Pick the decimal places and copy
Under the “Result”, tap 0 to 3 in “Decimal places (rounded)”. Tap the copy button to the right of a result to copy just the number (like “667”).
Under the “Result”, click 0 to 3 in “Decimal places (rounded)”. Click the copy button to the right of a result to copy just the number (like “667”).
Handy for
Checking a sale price
For “30% off 39.80”, enter the price and 30 to see both the discount and what you'll pay.
Shoppers
Year-over-year or month-over-month growth
Enter last year's and this year's figures to see how much they rose or fell, in percent and in absolute terms.
Office workers and shop owners
Test scores and completion rates
Enter something like “35 out of 42” to see the percentage you got and how much is left.
Students and teachers
Finding the price before a discount or tax
Work back from “800 after 20% off” to the original 1,000, or find the price before a markup.
People setting prices
Good to know before you start
- Results that don't divide evenly are rounded half up. If you need to round money down, use a tool that lets you choose, such as Tax Calculator (Add or Remove Tax).
- For chained calculations like “20% off, then another 10% off”, enter each step separately.
- It doesn't do interest, compound growth or statistics (averages, standard deviation and so on).
How percentages are calculated
A percent is a share out of 100. “X% of Y” is Y × X ÷ 100, and “X is what percent of Y” is X ÷ Y × 100. Percent change is (new − old) ÷ old × 100: positive when the number goes up, negative when it goes down.
Working backwards is where people slip up. The original price of something that costs 800 after 20% off is not 800 × 1.2 = 960 but 800 ÷ 0.8 = 1,000. Likewise, a 50% rise followed by a 50% drop doesn't get you back to the start: you end up at 75%. This tool keeps every calculation as an exact fraction and only rounds at the end, so there are no floating-point errors.
Frequently asked questions
Common questions about working with percentages.
Are the numbers I enter sent anywhere?
No. Everything is calculated inside the browser on your device, and nothing you type is sent to a server.
How do I work out a discounted price?
Choose “What is X% of Y?” and enter the original price and the discount percent. “Minus X%” is the price after the discount, and “X% of it” is the amount you save.
Can I get the original price from a discounted one?
Yes. Choose “Find the original”, enter the discounted price and the percent, and read “Before a 20% decrease” (for a 20% discount). For a price after a markup, read “Before a 20% increase”.
What's the difference between percent change and the difference?
The difference is the new value minus the old one (200 → 250 is +50). The percent change is that difference as a share of the old value (+25%).
What's the difference between percent and percentage points?
When you compare two percentages, the gap between them is measured in percentage points. If approval goes from 40% to 50%, it rose by 10 points, which is a 25% increase. Enter 40 and 50 in “Percent change” and you get +25% with a difference of +10 (points).
Why is there no percent change when the old value is 0?
Percent change divides by the old value, and you can't divide by 0. In that case only the difference is shown.
How are results that don't divide evenly shown?
They're rounded half up to the number of places you choose in “Decimal places (rounded)” and marked with “≈”. Results that come out exactly are shown as they are (30, not 30.00).
Can I enter negative numbers or decimals?
Yes. Decimals up to 6 places and negative numbers both work. Thousands separators like “1,000” and symbols like “$” or “%” are ignored.
What exactly gets copied?
The button next to a result copies a plain number without separators or “≈” (like “1234.5”), so you can paste it straight into a spreadsheet or a form.
Is it free?
Yes. No sign-up and no ads.
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