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Allele Frequency Calculator
Calculate allele frequencies and genotype distributions in populations using Hardy-Weinberg principles.
Reviewed by the calculator.uk.com Team · Last reviewed 18 July 2026 · Our methodology
Enter population data to calculate allele frequencies and expected genotype distribution
The Allele Frequency Calculator is a powerful tool for population genetics analysis that helps determine the frequency of different alleles (gene variants) in a population. It uses the Hardy-Weinberg principle to analyze genetic variation and predict genotype distributions in populations.
Calculating Allele Frequencies
For a gene with two alleles (A and a), the calculator determines frequencies using this formula: p (frequency of A) = (2 × AA + Aa) ÷ (2 × total population) q (frequency of a) = (2 × aa + Aa) ÷ (2 × total population) where p + q = 1
Hardy-Weinberg Equilibrium
The calculator uses Hardy-Weinberg equations to predict genotype frequencies: AA (p²) = frequency of homozygous dominant Aa (2pq) = frequency of heterozygous aa (q²) = frequency of homozygous recessive
The calculator provides comprehensive insights into the genetic composition of a population. Understanding these results is crucial for population genetics studies, breeding programs, and genetic disorder research.
Allele Frequencies
Allele frequencies (p and q) indicate the proportion of each allele in the population. A frequency of 0.7 means that 70% of all alleles in the population are of that type. These frequencies help predict the likelihood of specific genotypes appearing in offspring.
Expected Genotype Distribution
The expected genotype numbers show the theoretical distribution of genotypes if the population is in Hardy-Weinberg equilibrium. Comparing actual numbers to expected ones can reveal whether the population is evolving or experiencing selective pressures.
1. What is an allele frequency?
Allele frequency is the proportion of a particular allele (variant of a gene) among all alleles at that gene locus in a population. It's expressed as a decimal or percentage and represents how common that allele is in the population.
2. What does Hardy-Weinberg equilibrium mean?
Hardy-Weinberg equilibrium is a state where allele and genotype frequencies remain constant from generation to generation, assuming no evolutionary forces are acting on the population (no mutation, migration, selection, or genetic drift).
3. Why are my expected genotype numbers different from the actual counts?
Differences between observed and expected numbers might indicate that your population is not in Hardy-Weinberg equilibrium. This could be due to natural selection, non-random mating, mutation, migration, or genetic drift.
4. What does the heterozygous frequency tell us?
The heterozygous frequency (2pq) represents the proportion of individuals carrying two different alleles of the gene. This is important for understanding genetic variation and the potential for passing different alleles to offspring.
5. What is the scientific source for this calculator?
This calculator applies the Hardy-Weinberg principle (p² + 2pq + q² = 1), independently derived by G.H. Hardy and Wilhelm Weinberg in 1908, which predicts genotype frequencies in a population from allele frequencies under idealised conditions (random mating, no selection, mutation, migration, or drift). It's the foundational model used throughout population genetics to detect whether a real population deviates from these assumptions.