How to Find the Percentage of a Number
Finding the percentage of a number is one of the most common calculations in everyday life — it comes up when you're splitting a restaurant bill, working out sales tax at the register, or checking how much interest a savings account paid out. Rather than guessing, the calculation reduces to one simple ratio: take the percentage, divide it by 100 to turn it into a decimal, and multiply that decimal by the number you're starting with. Once you're comfortable with that pattern, you can apply it to virtually any percentage-of-value problem, from a 20% tip to a 7% sales tax to a 3.5% raise on your salary.
When Would I Find the Percentage of a Number?
- Sales tax: Working out state or country sales taxes on purchases.
- Gratuity tips: Calculating tipping amounts for food and delivery services.
- Financial portfolios: Defining absolute asset allocations based on target percentages.
Worked Example: Sales Tax
To calculate 15% of $120 (for example, a 15% sales tax on a $120 purchase):
- Multiply 15 by 120: 15 × 120 = 1800
- Divide by 100: 1800 / 100 = $18.
Worked Example: Restaurant Tip
Suppose your restaurant bill comes to $84 and you want to leave a 20% tip:
- Multiply 20 by 84: 20 × 84 = 1680
- Divide by 100: 1680 / 100 = $16.80 tip.
- Total to pay: $84 + $16.80 = $100.80.
Percentage of a Number FAQ
Q: How do I calculate a percentage of a number in Excel?
Write the formula =Number*(Percentage/100) or simply =Number*PercentageCell (where the percentage cell is formatted as a percentage).
Q: What is 15 percent of 100?
Multiply 100 by 15 and divide by 100, which yields 15.
Q: Can the percentage be larger than 100?
Yes. For example, 150% of 200 equals 300. This occurs when you want to compute a portion that is larger than the original reference number.
Q: How do I quickly estimate a percentage in my head?
For round numbers like 10%, just move the decimal point one place left (10% of 250 is 25). For 20%, find 10% first and double it. For 5%, find 10% and halve it — these mental shortcuts cover most everyday tipping and discount scenarios.