Allele Frequency Calculator

Count alleles directly. The A count is two times the AA count plus the Aa count, because each AA individual carries two A copies and each Aa carries one. Divide that by the total allele pool, which is two times the number of individuals, to get freq A.

Each individual at this locus is diploid and carries two alleles, so a population of N individuals holds 2N allele copies. That 2N pool is the denominator for both frequencies, which is why 500 people give a pool of 1000 alleles.

Yes. With only two alleles, every copy in the pool is either A or a, so freq A plus freq a always equals one. If your numbers do not sum to one, recheck the counts you entered.

Frequencies are rounded to nine decimal places, so a value like five sixths shows as 0.833333333 rather than a longer repeating decimal. The underlying arithmetic is exact integer counting, and only the display is trimmed.

No, this is the first step. This tool counts the alleles you actually observed. Hardy-Weinberg then predicts the expected genotype frequencies, p squared, 2pq and q squared, from those allele frequencies under a set of idealized assumptions.

You cannot split a dominant phenotype into AA and Aa from counts alone, because both look the same. You either need genotyping data, or you must assume Hardy-Weinberg equilibrium and estimate the split from the recessive frequency.

Yes, any single count can be zero, such as a locus where no recessive homozygotes appear. The only rule is that the three counts cannot all be zero, since an empty population has no alleles to measure.

No, this calculator is built for a single locus with exactly two alleles, A and a. Loci with three or more alleles need a separate approach that counts each allelic type against the same 2N pool.

No. The counting and division happen entirely in your browser, so the genotype numbers you enter never leave your device and nothing is stored on a server.