Determining the average of two percentages is a little different to calculating the average of any two numbers. You can't just add the percentages and divide them by two to get the answer. Because the percentages could be based on different sample sizes, this simple method would lead to an inaccurate result. You need to find the real numbers represented by each percentage, add them together, divide this by the combined total of both of the original samples, and then multiply by 100 to turn the result into an averaged percentage
Convert the two percentages into decimals. For example, suppose you want to calculate the average of 60 percent of 200 and 40 percent of 100. Convert these values into decimals by dividing them by 100, so you get 0.6 and 0.4.
Multiply each decimal by the number in that sample. So 0.6 × 200 = 120 and 0.4 × 100 = 40.
Add the two numbers the percentages represented together: 120 + 40 = 160. Then add the two total sample sizes together: 200 + 100 = 300.
Divide the total number represented by the original percentages by the total sample size: 160 ÷ 300 = 0.533. Multiply the answer by 100 to get the result as a percentage. Multiplying 0.533 by 100 gives you 53.3 percent.
