Everyday tool
Percentage Calculator
Six percentage calculators in one page: X% of Y, what percent, percentage change, increase, decrease and reverse percentage. Instant answers, no sign-up.
Free, no sign-up. Runs in your browser; nothing is uploaded.
What is X% of Y?
Find a percentage of a number.
36
X is what percent of Y?
Express one number as a percentage of another.
15%
Percentage change
How much a value rose or fell, as a percent of where it started.
+25% increase
Increase a number by X%
Add a percentage, such as a markup or tax.
280
Decrease a number by X%
Take a percentage off, such as a discount.
220
Find the original value
Work backwards from a result after a percentage change.
250
How to use the percentage calculator
Percentages without the mental maths
A percentage is just a number out of 100, but the same few questions come up again and again: how much is 15% of this bill, what share is this of that total, how far did the price move. This page puts the six common forms side by side so you never have to remember which way round the formula goes.
The six calculators
- What is X% of Y? Handy for tips, commission, VAT and discounts. The result is Y x X / 100.
- X is what percent of Y? Turns a part and a whole into a share, such as 36 of 240 being 15%.
- Percentage change compares an old value with a new one. A positive result is an increase, a negative one a decrease.
- Increase by X% adds a percentage to a number, for a markup or a price rise.
- Decrease by X% takes a percentage off, for a discount or a cut.
- Find the original value works backwards from the result of a change, so you can see what a price was before tax or before a sale.
Using it
Every card has two or three fields with a sensible example already filled in. Change the numbers and the answer updates immediately; commas are fine. Use the Copy button on any card to put the result on your clipboard.
Common traps
- Order matters. A 20% rise followed by a 20% fall does not return you to the start: 100 becomes 120, then 96.
- Percent of what? Always check the base. A margin is a percentage of the selling price, while a markup is a percentage of the cost.
- Percent versus points. A rise from 10% to 12% is two percentage points, or a 20% relative increase.
- Rounding. Results show up to four decimals, which is more than enough for everyday use. Round the final figure to the precision you need.
Where to go next
For shop prices use the discount and sale price calculator, and for margins use the profit margin and markup calculator. All the maths runs in your browser and nothing you type is sent anywhere.
Frequently asked questions
How do I calculate X% of a number?
Multiply the number by X and divide by 100. For example, 15% of 240 is 240 x 15 / 100 = 36. The first card does this for you as you type.
How is percentage change calculated?
Subtract the starting value from the new value, divide by the starting value and multiply by 100. Going from 80 to 100 is +25%, but going back from 100 to 80 is -20%, because each change is measured against a different starting point.
What is the difference between percent and percentage points?
If an interest rate moves from 4% to 5%, that is one percentage point, but a 25% relative increase. Use the percentage change card for the relative figure and simple subtraction for points.
How do I find the original price before a discount or tax?
Use the reverse card. Divide the final value by (1 + rate) for an increase, or by (1 - rate) for a decrease. A price of 280 after a 12% increase started at 250.
Why can percentage change not be calculated from zero?
The formula divides by the starting value, and nothing can be divided by zero. A change from 0 to any other number has no defined percentage, so the tool tells you instead of showing a misleading figure.