How to Work Out a Percentage Using a Calculator

The percentage button for this calculator is on the right-hand side.

You can use a calculator to easily figure out percentages. The term "percentage" refers to a portion out of 100. For example, one-half is equal to 50 percent, or 50 out of 100. The three variables in a percentage calculation are the part, the whole, and the percentage. In the equation: 25% of 40 = 10, 10 is the part, 40 is the whole, and 25 is the percentage. In each of the three types of percentage calculations, you must find a different omitted variable.

Instructions

1. Determine which variable is omitted in the calculation you are trying to solve. If the question is "What percentage of 40 is 10?" the omitted variable is the percentage. If the question is "What is 25 percent of 40?" the omitted variable is the part. If the question is "10 is 25 percent of what?" the omitted variable is the whole.

2. If the omitted variable is the percentage, divide the part by the whole using your calculator to determine the answer. For the example equation, this is 10 ÷ 40 = 0.25. If your calculator has a percentage button, press it to determine the percentage. If your calculator does not have such a button, multiply your previous answer by 100 to determine the percentage: 0.25 x 100 = 25%.

3. If the omitted variable is the part, use the calculator to multiply the whole by the percentage to determine the answer. If your calculator has a percentage button, the calculation is as follows: 40 x 25% = 10. If your calculator does not have a percentage button, you must first divide the percentage by 100: 25 ÷ 100 = 0.25. You can then multiply this answer by the whole to determine the part: 0.25 x 40 = 10.

4. If the omitted variable is the whole, divide the part by the percentage to determine the answer. If your calculator has a percentage button, the calculation is as follows: 10 ÷ 25% = 40. If your calculator does not have a percentage button, you must divide the percentage by 100 before completing the calculation: 25 ÷ 100 = 0.25. You can then divide the part by this answer to determine the whole: 10 ÷ 0.25 = 40.

Tips & Warnings

• Double-check your answer, particularly if it seems unlikely. You may have made a calculation error at some point.

References

• "The complete how to figure it"; Darrell Huff, Carolyn R. Kinsey; 1996.

Resources

• Read this Article in Spanish