Formula to calculate a percentage
To calculate what percentage a part is of a whole, divide the part by the whole and multiply by 100. The whole must be greater than zero. For example, 18 correct answers out of 24 gives (18 ÷ 24) × 100 = 75%.
To calculate a percentage of an amount, multiply the amount by the rate and divide by 100. For example, 15% of 240 is 240 × 15 ÷ 100 = 36. For percentage change, use ((new value − original value) ÷ original value) × 100.
Use the Percentage Calculator for percent of a number, percentage ratios and percentage change. For an increase or reduction, open the Add or Subtract Percentage Calculator.
Formula for percentage in Excel
If cell B2 contains the part and C2 contains the total, enter =B2/C2 and format the result as Percentage. For example, 18 divided by 24 displays as 75%. If the rate is stored in B2 as 15%, calculate 15% of an amount in A2 with =A2*B2. If B2 contains the number 15, use =A2*B2/100.
For percentage increase in Excel, use =(new_value-old_value)/old_value and format the result as Percentage. Replace the names with cell references, such as =(C2-B2)/B2. Check that the old value is not zero.
Formula to highlight duplicates in Google Sheets
To highlight duplicate values in column A, select the range A2:A, open Format → Conditional formatting, choose “Custom formula is,” and enter =COUNTIF($A$2:$A,A2)>1. The formula highlights every value that appears more than once.
Formula to remove duplicates in Excel
In Microsoft 365, enter =UNIQUE(A2:A100) in an empty cell to return a list containing each value once. This creates a separate result and leaves the original data in place. To remove duplicates from the original range, use Data → Remove Duplicates and review the selected columns before confirming.
In Excel conditional formatting, =COUNTIF($A:$A,A2)>1 highlights all repeated values in column A. Use =COUNTIF($A$2:A2,A2)>1 when you want to mark only repeated occurrences after the first.
Formula for standard deviation
Standard deviation describes how spread out the values are around their mean. Use the population formula when your list contains the entire group you are measuring. Use the sample formula when your data are a subset of a larger group.
Sample: s = √(Σ(x − x̄)² ÷ (n − 1))
For the values 2, 4, 4, 4, 5, 5, 7, and 9, the mean is 5 and the population standard deviation is 2. The sample standard deviation for the same eight values is about 2.14. In Excel, use =STDEV.P(A2:A9) for a population or =STDEV.S(A2:A9) for a sample.
Use the Variance and Standard Deviation Calculator for either method, or the Statistics Calculator for a broader summary of a data set.
Formula for average
The arithmetic average, also called the mean, is the total of all values divided by how many values there are.
For 10, 15, and 20, the sum is 45 and there are three values, so the average is 45 ÷ 3 = 15. The mean can be affected by unusually high or low values; the median is a different measure of center.
Paste your list into the Average Calculator to calculate the mean and review the result.
Formula for converting Celsius into Fahrenheit
The formula to convert Celsius to Fahrenheit is (Celsius × 9 ÷ 5) + 32. Multiply the Celsius temperature by 9/5, then add 32.
For example, 25°C is (25 × 9 ÷ 5) + 32 = 77°F. To convert Fahrenheit to Celsius, reverse the steps: °C = (°F − 32) × 5 ÷ 9. The 32-degree offset is why a direct 9/5 multiplication alone is not enough.
Use the Temperature Conversion Calculator to convert Celsius, Fahrenheit and Kelvin.
Formula to find the area of a triangle
A quick way to remember the formula for area of a triangle is to multiply the base by the perpendicular height and divide by two. The height must meet the base at a right angle; a sloped side is not automatically the height.
For a base of 12 units and a perpendicular height of 7 units, area = (12 × 7) ÷ 2 = 42 square units. Use the Triangle Area Calculator to calculate an area from a base and height or choose another supported method.
Frequently asked questions
What is the formula for percentage?
Percentage = (part ÷ whole) × 100. To find a percentage of a value, multiply the value by the rate and divide by 100.
What is the formula for standard deviation?
For a population, standard deviation is the square root of the sum of squared differences from the mean divided by N. For a sample, divide by n − 1 before taking the square root.
What is the formula for average?
Arithmetic average = sum of values ÷ number of values.
What is the formula for converting Celsius into Fahrenheit?
°F = (°C × 9 ÷ 5) + 32.
What is the formula for the area of a triangle?
Area = (base × perpendicular height) ÷ 2.
Can an Excel formula remove duplicates?
In Microsoft 365, =UNIQUE(A2:A100) returns a distinct list in another range. To delete duplicate entries in place, use Data → Remove Duplicates.
Use the linked tools to check your inputs, keep the right units and compare your result with the worked examples above.