Calculate allele and genotype frequencies under Hardy-Weinberg equilibrium. Test populations for evolutionary forces.
For a diploid population with two alleles, this calculator converts allele frequencies into the Hardy-Weinberg genotype proportions p^2, 2pq, and q^2. It can also compare observed genotype counts with the counts expected from their estimated allele frequencies. The most common mistake is using pq for the heterozygote frequency; because either allele can come from either parent, the expected frequency is 2pq. Expected proportions describe an equilibrium model, not a guarantee about the genotypes observed in a sample.
A concrete input and expected output from the current implementation.
Input
Allele A frequency (p): 0.60 Allele a frequency (q): 0.40
Expected output
Expected AA frequency: 0.36 (36%) Expected Aa frequency: 0.48 (48%) Expected aa frequency: 0.16 (16%)
The three frequencies are p^2 = 0.60^2 = 0.36, 2pq = 2 x 0.60 x 0.40 = 0.48, and q^2 = 0.40^2 = 0.16. They sum to 1.00.
The two allele frequencies are represented by p and q, with p + q = 1 for a two-allele locus. Hardy-Weinberg equilibrium predicts homozygote frequencies of p^2 and q^2 and a heterozygote frequency of 2pq. Multiplying each frequency by population or sample size gives its corresponding expected genotype count.
For observed counts nAA, nAa, and naa in a sample of N individuals, p is calculated as (2nAA + nAa) / (2N), while q is (2naa + nAa) / (2N). Expected counts are then Np^2, N(2pq), and Nq^2. Comparing those expectations with the observed counts indicates how closely the sample fits equilibrium.
No. It can show whether observed genotype frequencies differ from the proportions predicted by Hardy-Weinberg equilibrium, but that difference is not diagnostic of one cause. Identifying a cause requires study design, biological context, replicate samples, and checks for population structure, related individuals, sampling effects, and genotype quality.
Only if the recessive phenotype reliably represents the aa genotype and Hardy-Weinberg equilibrium is a defensible assumption. In that case the phenotype frequency is q^2, so q is its square root and p = 1 - q. Without those conditions, taking the square root can give a misleading allele-frequency estimate.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
Calculate percentages, percentage change, and what percent one number is of another with step-by-step breakdowns.
Calculate tips and split bills between multiple people with customizable tip percentages and rounding options.
Calculate monthly payments, total interest, and generate amortization schedules for loans and mortgages.
Calculate Body Mass Index from height and weight with category classification and healthy range guidance.
Calculate sale prices, savings amounts, and final costs after single or stacked percentage discounts.
Compute mean, median, mode, standard deviation, variance, and other descriptive statistics from a data set.