#### Step

Convert the APY to a decimal by dividing by 100. For example, if your APY is 2.4 percent, you would divide 2.4 by 100 to get 0.024.

#### Step

Add 1 to the APY expressed as a decimal. In this example, you would add 1 to 0.024 to get 1.024.

#### Step

Raise the result from step 2 to the 1/12 power using the calculator, since there are 12 times when interest is compounded per year. In this example, you would raise 1.024 to the 1/12th power to get 1.001978332.

#### Step

Subtract 1 from the result from step 3 to calculate the monthly rate expressed as a decimal. In this example, you would subtract 1 from 1.001978332 to get 0.001978332.

#### Step

Multiply the result from step 4 by 100 to convert the monthly rate from a decimal to a percentage. Finishing the example, you would multiply 100 by 0.001978332 to find the monthly interest rate to be 0.1978332 percent.