Freq. Hardy-Weinberg
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
p² + 2pq + q² = 1
About this calculator
The Hardy-Weinberg Expected calculator estimates genotype frequencies in a population based on allele frequencies. It uses the formula p² + 2pq + q² = 1, where p and q represent dominant and recessive allele frequencies. This tool is used in population genetics to predict theoretical distributions under ideal conditions (genetic equilibrium).
The formula assumes a large population with random mating, no migration, mutation, or natural selection. Each term (p², 2pq, q²) corresponds to dominant homozygous, heterozygous, and recessive homozygous genotypes. To use the calculator, input the allele frequencies (p and q) to obtain theoretical proportions.
This tool is useful for analyzing deviations from equilibrium, such as in studies of inbreeding or gene flow. For example, in medical genetics, it helps estimate recessive disease burdens in populations. However, most real populations do not meet all model assumptions, limiting result accuracy.
Cautions: results are theoretical approximations. If mutation, selection, or genetic drift are present, actual distributions may differ. Comparing expected values with observed data is recommended to test hypotheses about population dynamics.
Frequently asked questions
What does the Hardy-Weinberg calculator do?
It calculates expected genotype frequencies (p², 2pq, q²) based on allele frequencies (p and q), assuming theoretical genetic equilibrium.
When should I use it?
Use it to predict genotype distributions in theoretical populations or compare with real data to detect deviations (like natural selection).
What does each term in the formula mean?
p² = dominant homozygous, 2pq = heterozygous, q² = recessive homozygous. Together, they sum to 100% of the population.
Why might results differ from observed data?
The formula assumes ideal conditions (no migration, mutation, or selection). Real populations rarely meet all criteria, causing discrepancies.
How to calculate p and q from real data?
Count alleles in a population sample. For a recessive allele, q² is the frequency of recessive homozygotes, and q = √q².