Percentage Calculator
Calculate X% of Y, what percent one number is of another, percentage change, increase or decrease and the original value. Exact decimals with worked steps.
How to use Percentage Calculator
- 1Pick the question you want answered from the Mode buttons, or tap a common question.
- 2Enter the two numbers; commas and spaces in pasted numbers are fine.
- 3Read the result and the worked steps, then copy them.
What makes it better
- Five modes on one page: X% of Y, X is what % of Y, percentage change, increase or decrease by %, and reverse percentage
- A worked step-by-step line for every answer, ready to copy
- Exact decimal arithmetic with a precision setting, and a message whenever a result is rounded
- Clear messages for a zero denominator instead of Infinity or NaN
- Quick-fill buttons for a 15% tip, a 25% discount and adding or removing a VAT-style percentage
About Percentage Calculator
This percentage calculator answers the five questions people ask most: what is X% of Y, X is what percent of Y, how much did a value change in percent, what is a value after an increase or decrease, and what was the original before a percentage was added or removed. Every answer comes with a worked line such as 20% of 150 = 20 ÷ 100 × 150 = 30, and the arithmetic is exact, so you never see 0.30000000000000004.
Common uses
- Work out a 15% tip or a 30% discount on a shopping bill.
- Find the percentage change between last month's and this month's figures.
- Recover the original price when you only know the sale price and the discount.
- Check homework or exam marks, for example 42 out of 60 as a percentage.
Example
Input
20, 150
Result
20% of 150 = 20 ÷ 100 × 150 = 30
Good to know
- This is a general percentage calculator. It does not know tax rates, GST slabs or inclusive and exclusive rules for a country; use a dedicated tax calculator for those.
- Percentage change divides by the old value, so it is undefined when the old value is 0. If the old value is negative the change is measured against its absolute value, so going from -50 to -25 counts as a 50% increase.
- Results are rounded half away from zero to the precision you choose (4 decimal places by default, up to 12), and the page tells you when digits were dropped. Commas are read as thousands separators, not decimal commas.
Percentage Calculator FAQ
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For 20% of 150 that is 20 ÷ 100 × 150 = 30. In the X% of Y mode, enter 20 and 150 and the page writes this working out for you.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For 30 out of 150 that is 30 ÷ 150 × 100 = 20%. If the whole is 0 the question has no answer, and the page says so instead of showing an error value.
What is the formula for percentage change?
Subtract the old value from the new one, divide by the old value and multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%. A negative result means a decrease.
How do I get the original price after a discount or increase?
Divide the final price by one plus the increase, or by one minus the decrease, written as a decimal. If a price is 120 after a 20% rise, the original was 120 ÷ 1.2 = 100. Use the Reverse mode for this.
Why is a 50% increase followed by a 50% decrease not back to the start?
Each percentage applies to a different base. 100 plus 50% is 150, and 50% of 150 is 75, so you finish 25% below where you began. Run both steps in the Increase / decrease mode to see the numbers.