Convert the two percentages into decimals. Assume you want to calculate the average of 60 percent and 40 percent. Convert these values into decimals by dividing them by 100, so you get 0.6 and 0.4.
Find the sum of the two decimal values. In this example, adding 0.6 and 0.4 gives you 1.
Divide the resulting value by 2 to get 0.5.
Multiply the answer by 100 to get the answer in percentage. Multiplying 0.5 by 100 gives you 50 percent.