Calculating allele frequencies in a gene pool1. To calculate the frequency of the brown allele, count the number of BROWN ALLELES and divide by the total number of alleles in this population2. In this beetle population, the number of brown alleles is 83. In this beetle population, the total number of alleles for color is 204. The frequency of the brown allele in this beetle population is .45. The frequency of the green allele in this beetle population is .6