To find a percentage of a number, convert the percentage to a decimal and multiply it by the number. For example, 15% of 240 is calculated as 0.15 × 240, which equals 36. The same method works for discounts, tax, tips, commissions, markups, savings goals, and many other everyday calculations.
Enter a percentage and a number to calculate the percentage amount without converting the values manually.
Fifteen percent becomes 0.15. Multiplying 0.15 by 240 gives a percentage amount of 36.
What “Percentage of a Number” Means
Finding a percentage of a number means calculating a selected share of that number. The percentage describes the size of the share out of every 100 equal parts.
For example, 25% means 25 out of 100, which is the same as one quarter. Therefore, 25% of 80 is one quarter of 80, or 20.
This type of percentage problem is different from asking what percentage one number is of another. Here, the percentage and base number are known, and the percentage amount is unknown.
The Percentage-of-a-Number Formula
Convert the percentage into decimal form by dividing it by 100. Then multiply the decimal by the base number.
The base number is the full amount from which the percentage share is being calculated.
The answer is an amount in the same unit as the base number. If the base number is dollars, the answer is dollars. If it is kilograms, the answer is kilograms.
Worked Example: Find 15% of 240
Begin by converting 15% to decimal form. Divide 15 by 100 to get 0.15.
Multiply 0.15 by 240. The result is 36.
Therefore, 15% of 240 is 36.
Method 1: Convert the Percentage to a Decimal
Dividing a percentage by 100 moves the decimal point two places to the left. Twenty percent becomes 0.20, 7% becomes 0.07, and 2.5% becomes 0.025.
After conversion, multiply by the base number. To find 7% of 450, calculate 0.07 × 450, which equals 31.5.
This is the most flexible method because it works with whole percentages, decimal percentages, and percentages above 100.
Method 2: Use the Percentage as a Fraction
A percentage can also be written as a fraction over 100. For example, 15% is 15/100.
Multiply the number by the numerator and divide by 100. For 15% of 240, calculate 240 × 15 ÷ 100.
The fraction method is mathematically identical to the decimal method and may be easier when working by hand.
Method 3: Use Easy Percentage Benchmarks
Some percentages can be calculated quickly from familiar benchmarks. Ten percent is found by dividing by 10, while 1% is found by dividing by 100.
To find 15%, calculate 10% and 5%, then add them. For 240, 10% is 24 and 5% is 12, so 15% is 36.
Other useful benchmarks include 50% as one half, 25% as one quarter, and 75% as three quarters.
How to Find a Percentage of a Number on a Calculator
Enter the percentage as a decimal and multiply by the number. For 18% of 350, enter 0.18 × 350 to get 63.
You can also enter 18 ÷ 100 × 350. Both expressions give the same result.
The Percentage Calculator lets you enter the percentage and base number directly, reducing the chance of an incorrect decimal conversion.
Finding a Discount Amount
A discount amount is a percentage of the original price. To find a 20% discount on a $75 item, calculate 0.20 × 75.
The discount is $15. Subtract the discount from the original price to find the sale price: $75 − $15 = $60.
The percentage amount and the final reduced amount are different results, so check which one the question requires.
Finding Tax, Tips, and Service Charges
Tax, tips, and service charges are often calculated as percentages of a bill or purchase amount.
For a 12% service charge on $80, calculate 0.12 × 80 to get $9.60. Add the charge to the original amount for a total of $89.60.
Confirm whether the percentage applies before or after other charges, discounts, or taxes because the base amount can change.
Finding Commission or Profit Share
Commission calculations use the same multiplication formula. If a salesperson earns 6% of $4,500 in sales, calculate 0.06 × 4,500.
The commission is $270. If different commission rates apply to different sales categories, calculate each amount separately before adding them.
The percentage rate alone does not determine the payment; the correct base amount must also be identified.
Percentages Greater Than 100%
The formula also works for percentages above 100. To find 125% of 80, convert 125% to 1.25 and multiply by 80.
The result is 100. This represents the full original amount plus another 25% of it.
Percentages above 100 are common in target achievement, capacity comparisons, growth, and scaling.
Decimal Percentages
A percentage does not need to be a whole number. To find 2.5% of 600, convert 2.5% to 0.025.
Multiply 0.025 by 600 to get 15.
Take care when moving the decimal point. The decimal form of 2.5% is 0.025, not 0.25.
Common Mistakes
One mistake is multiplying by the percentage number without dividing by 100. Multiplying 240 by 15 gives 3,600, not 15% of 240.
Another mistake is subtracting the percentage amount when the question only asks for the amount itself. A discount amount and a discounted price are not the same.
Incorrect decimal placement and using the wrong base value are also common sources of error.
How to Check the Result
Estimate the answer before accepting it. Since 15% is less than 20%, 15% of 240 should be less than 48.
You can also reverse the calculation. Divide the result by the base number and multiply by 100. Dividing 36 by 240 and multiplying by 100 returns 15%.
This reverse check is especially useful when the original calculation includes decimal values.
Conclusion
To find a percentage of a number, divide the percentage by 100 and multiply by the number.
Use decimal multiplication for a general method, or combine familiar percentages such as 10%, 5%, 25%, and 50% for mental calculations.
Enter the values in the Percentage Calculator to calculate the percentage amount and confirm the formula.
Related percentage guides and calculators
FAQs
How do I find 15% of a number?
Convert 15% to 0.15 and multiply it by the number.
What is 15% of 240?
Fifteen percent of 240 is 36.
Can I calculate a percentage without decimals?
Yes. Multiply the number by the percentage and divide the result by 100.
How do I find a percentage greater than 100?
Use the same formula. For example, 125% becomes 1.25 before multiplication.