# Allele Frequency Calculator (p = (2AA + Aa) / 2N) Compute allele frequencies from genotype counts: p = (2AA + Aa) / 2N, q = (2aa + Aa) / 2N. Derived from Hartl & Clark 2007, Griffiths, StatPearls. Educational use only. > Canonical page: https://elysiatools.com/en/tools/allele-frequency-calculator - **Category:** Education - **Keywords:** allele frequency, allele frequency calculator, gene frequency, p frequency, q frequency, biallelic, genotype count, population genetics, genetics, biology ## Overview The Allele Frequency Calculator computes p and q for a biallelic locus from observed AA, Aa, and aa genotype counts. It reports the population size, total allele count, copies of each allele, and results rounded to your selected number of decimal places. Educational use only. ## Inputs - **AA count (homozygous dominant)** (number): Observed count of genotype AA. - **Aa count (heterozygous)** (number): Observed count of genotype Aa. - **aa count (homozygous recessive)** (number): Observed count of genotype aa. - **Decimal Places** (number) ## When to use - Calculate allele frequencies from observed genotype counts in a population genetics exercise. - Convert AA, Aa, and aa counts into allele-copy totals for a biallelic locus. - Check whether p and q sum to 1 using a consistent, repeatable calculation. ## How it works - Enter the observed counts for AA, Aa, and aa individuals. - The calculator determines N and the total number of alleles as 2N. - It calculates p with (2AA + Aa) / 2N and q with (2aa + Aa) / 2N. - The JSON result includes p, q, N, totalAlleles, countA, and counta, rounded to the selected decimal places. ## Use cases - Population genetics coursework involving allele and genotype frequencies. - Laboratory or field studies summarizing observed biallelic genotype counts. - Teaching demonstrations of how homozygotes and heterozygotes contribute allele copies. ## Frequently asked questions ### What inputs does the calculator require? Enter the observed counts for AA, Aa, and aa genotypes. ### How is allele frequency p calculated? p = (2AA + Aa) / 2N, where N is the total number of individuals. ### How is allele frequency q calculated? q = (2aa + Aa) / 2N. ### Why is the total allele count 2N? Each diploid individual carries two alleles at the locus, so N individuals provide 2N alleles. ### Can I control the number of decimal places? Yes. Decimal Places can be set from 0 to 8, with 4 as the default. ## Related tools - [Genotype Frequency Calculator](https://elysiatools.com/en/tools/genotype-frequency-calculator): Compute genotype frequencies from counts: freq = count / N. Also derives allele and phenotypic frequencies. Derived from Hartl & Clark 2007, Griffiths, StatPearls. Educational use only. - [Hardy-Weinberg Equilibrium Calculator (p² + 2pq + q² = 1)](https://elysiatools.com/en/tools/hardy-weinberg-equilibrium): Compute allele and expected genotype frequencies under Hardy-Weinberg equilibrium. 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