How to Figure Out Percenteges

You will find calculating percentages helpful in many aspects of your daily life.

Although calculating a percentage can be a daunting task for someone who avoids mathematics, percentages are a basic and useful tool. Applicable in many aspects of personal life, percentages play a key role in taxes, shopping, cooking and paying bills. While there are many different ways to determine a percentage, all percentage calculations express portions based on the number 100 as the full amount.

Things You'll Need

• Calculator

Instructions

Knowing the Percentage Up Front

1. Convert the percentage number (20 percent) into a decimal number. Move the decimal place over by two numbers. This will convert 20 percent into .20. All percentages can be expressed as a percentage (20 percent) or as a decimal (.20).

2. Identify the base number -- the number of which you need the percentage. For example, if you want to know what 20 percent of $400 is, 400 is your base number.

3. Multiply your decimal and your base number. For example, multiply .20 and 400. The result (80) is your answer. Therefore, $80 is 20 percent of $400.

Needing to Calculate the Percentage

1. Identify your base number and your partial number. For example, what percentage is 80 out of 400? In the example, 80 is your partial number and 400 is your base number.

2. Divide the partial number by the base number. In the example, you would calculate 80 divided by 400. The result will be the decimal version of the percentage. Here, that number is .20.

3. Convert the decimal into a percentage by moving the decimal point to the right by two spaces. This converts .20 into 20 percent.

Comparing to 100

1. Write down the known numbers as fractions. For example, using the statement that 20 percent of $400 is $80, you would write 80/400 and 20/100. If you don't know one of the numbers, leave it blank.

2. Cross multiply the numbers. Multiply 80 and 100. Multiply 400 and 20. These two calculations will equal each other -- 80 x 100 = 400 x 20.

3. Write the calculation even if you don't know all four numbers, using a question mark for the missing number. For example, ? x 100 = 400 x 20. Solve the calculation. In this example, you find the answer is 80 by dividing 8,000 by 100.

Tips & Warnings

• When using the cross calculation method, the base number for your percentage number is always 100. For example, 20 percent converts into 20/100.

References

• Helping With Math: Calculating Percentages