Percentage Calculator
This percentage calculator answers the three questions people ask most: what is X% of a number, what percent is one number of another, and what is the whole if you know a part and its percentage. Pick the question, enter two numbers and get the answer instantly. Use it for tips, sales tax, discounts, test scores and budgets.
Updated
Results
Results are estimates. See the methodology below.
How to use the percentage calculator
- Choose the question you want to answer:
- What is X% of Y? For example, 18% of a $64.50 check.
- X is what percent of Y? For example, 45 correct answers out of 60.
- X is Y% of what? For example, $30 saved is 15% of what original price.
- Enter X and Y. Type the numbers without the % sign; decimals and negative numbers are allowed.
- Read the result. The first and third questions return a number; the second returns a percentage.
Percentage formulas
"Percent" means "per hundred": the % sign stands for the number 0.01, so 18% is 18/100, or 0.18. Every percentage problem links three quantities, the part, the whole (the base) and the percentage:
part = percentage ÷ 100 × whole
The calculator rearranges this one relationship for each question:
| Question | Formula |
|---|---|
| What is X% of Y? | X × Y ÷ 100 |
| X is what percent of Y? | X ÷ Y × 100 |
| X is Y% of what? | X ÷ (Y ÷ 100) |
In the last two questions Y is in the denominator, so it can't be zero. Results are not rounded internally; round money amounts to the cent yourself.
Worked examples
1. Tip on a restaurant check
Your check is $64.50 and you want to leave 18%. Choose "What is X% of Y?", enter X = 18 and Y = 64.50: the tip is 11.61, or $11.61.
2. Sales tax on a purchase
A $89.99 pair of headphones with a 7.25% sales tax: X = 7.25, Y = 89.99 gives 6.524275, so the tax is about $6.52. Local rates vary, so check your receipt for the exact rate.
3. Test score as a percentage
You got 45 out of 60 questions right. Choose "X is what percent of Y?" with X = 45 and Y = 60: your score is 75%. With 27 out of 40, it would be 67.5%.
4. Finding the original price
A coupon saved you $30, and the store says that was 15% off. Choose "X is Y% of what?" with X = 30 and Y = 15: the original price was 200, so $200.
Common percentage mistakes
- Using the wrong base. "20% of what?" always refers to the whole. A price raised by 25% and then cut by 25% does not return to where it started, because the second percentage is taken of a larger base.
- Percent vs. percentage points. A rate rising from 4% to 5% has gone up 1 percentage point, which is a 25% relative increase.
- Adding discounts. Two successive discounts of 20% and 10% are not 30% off; each applies to the already reduced price.
Frequently asked questions
How do I calculate a percentage of a number in my head?
Find 10% by moving the decimal point one place to the left, then build from there. For 18% of $64.50, 10% is $6.45, so 20% is $12.90 and 18% is a little less. The calculator gives the exact figure.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. For 45 out of 60, 45 ÷ 60 = 0.75, which is 75%. Choose "X is what percent of Y?" to do it automatically.
How do I find the original number from a percentage?
Divide the part by the percentage expressed as a decimal. If $30 is 15% of a price, the price is 30 ÷ 0.15. That is the "X is Y% of what?" mode.
Can a percentage be more than 100%?
Yes. It means the part is larger than the whole you are comparing it with. If sales grow from 40 units to 90, this year's sales are 225% of last year's, which is an increase of 125%.
How do I calculate a percentage increase or decrease?
Subtract the old value from the new one, divide by the old value and multiply by 100. You can also use "X is what percent of Y?" with the new value as X and the old one as Y, then subtract 100 from the result.
Sources
Results are exact calculations from the numbers you enter and are rounded only for display. For taxes, interest or official figures, use the rates and rounding rules that apply to you.