Punnett Square Calculator

This tool fills in the Punnett square for a cross between two parents and counts what comes out of it. Enter each parent's genotype, either two alleles of one gene such as Aa or four alleles of two genes such as AaBb, and it draws the grid and returns the genotype ratio, the phenotype ratio and the percentage for each outcome. The one-gene form also handles incomplete dominance and codominance, where the heterozygote is its own phenotype rather than hidden behind the dominant allele. The two-gene form assumes the genes assort independently, so linked genes and gene interactions such as epistasis will not follow the 9 : 3 : 3 : 1 pattern it produces.