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Allele Frequency Calculator

Biology

Calculate allele frequencies p and q from genotype counts (AA, Aa, aa) in a population. Get exact allele proportions instantly for genetics coursework.

320
480
200

Dominant Allele Frequency (p)

56.00%
Recessive Allele Frequency (q)
44.00%
Total Individuals
1,000
Total Alleles Counted
2,000

This calculator computes your Dominant Allele Frequency (p), Recessive Allele Frequency (q), Total Individuals, Total Alleles Counted from the values you enter.

Inputs
Homozygous Dominant (AA) CountHeterozygous (Aa) CountHomozygous Recessive (aa) Count
Outputs
Dominant Allele Frequency (p)Recessive Allele Frequency (q)Total IndividualsTotal Alleles Counted

What is a Allele Frequency?

The Allele Frequency Calculator computes the frequency of the dominant allele (p) and recessive allele (q) in a population directly from genotype counts. Enter the number of homozygous dominant (AA), heterozygous (Aa), and homozygous recessive (aa) individuals, and the calculator returns the exact allele proportions.

This is the reverse direction of the Hardy-Weinberg Calculator, which starts from an allele frequency and predicts genotype frequencies — here, you start from real observed genotype counts and work backward to the underlying allele frequencies.

How to use this Allele Frequency calculator

  1. Enter the homozygous dominant (AA) count — the number of individuals in your sample or population carrying two dominant alleles.

  2. Enter the heterozygous (Aa) count — the number of individuals carrying one dominant and one recessive allele.

  3. Enter the homozygous recessive (aa) count — the number of individuals carrying two recessive alleles.

  4. Read the allele frequencies — p (dominant) and q (recessive), expressed as percentages, along with total individuals and total alleles counted.

Formula & Methodology

Allele frequency formulas:
p = (2 × AA count + Aa count) ÷ (2 × total individuals)
q = (2 × aa count + Aa count) ÷ (2 × total individuals)

Variable definitions:
- AA, Aa, aa — counts of each genotype observed in the population
- Total individuals — AA + Aa + aa
- Total alleles — 2 × total individuals (each individual carries 2 alleles for this gene)
- p — frequency of the dominant allele
- q — frequency of the recessive allele (always 1 − p)

Worked example:

Given AA = 320, Aa = 480, aa = 200 (1,000 individuals total):

Total alleles = 1,000 × 2 = 2,000

Dominant allele count = (320 × 2) + 480 = 1,120

p = 1,120 ÷ 2,000 = 56%

q = 1 − 0.56 = 44%

Note: This calculator assumes a single gene locus with exactly two alleles (dominant/recessive). For genes with more than two alleles, or for X-linked genes with different counting rules by sex, the underlying counting logic needs to be adapted accordingly.

Frequently Asked Questions

Allele frequency is calculated by counting every copy of each allele across the population: each homozygous individual (AA or aa) contributes 2 copies of that allele, while each heterozygous individual (Aa) contributes 1 copy of each allele. Dividing the count of a given allele by the total number of alleles (2 × total individuals) gives its frequency.
Allele frequency (p or q) is the proportion of all gene copies in the population that are a specific allele, while genotype frequency is the proportion of individuals with a specific genotype (like AA, Aa, or aa). This calculator computes allele frequencies directly from genotype counts, which is the reverse of the Hardy-Weinberg calculation.
In a two-allele system, every gene copy in the population must be either the dominant (p) or recessive (q) allele, so their frequencies necessarily sum to 1 (100%) — there is no third option for that gene locus.
Yes — after finding p and q here, plug them into the [Hardy-Weinberg Calculator](/hardy-weinberg-calculator/) to get the expected genotype frequencies (p², 2pq, q²), then compare those predictions against your actual observed genotype counts to see how closely the population matches equilibrium expectations.
This calculator handles the standard two-allele case (dominant/recessive). For genes with three or more alleles (like ABO blood type), you would need to count each allele's total copies separately across all genotype combinations and divide by the total allele count, following the same underlying logic.
Larger sample sizes give more statistically reliable frequency estimates, since small populations are more prone to sampling error and genetic drift. A count of a few dozen individuals will give an estimate, but population genetics studies typically use hundreds or thousands of individuals for confidence in the result.
Researchers commonly genotype a sample of individuals from a wild or clinical population, tally the AA/Aa/aa counts, and calculate allele frequencies as a first step before testing for Hardy-Weinberg equilibrium, estimating carrier rates for genetic conditions, or tracking allele frequency changes over generations (a signal of evolution).
If a population has 320 AA, 480 Aa, and 200 aa individuals (1,000 total, 2,000 total alleles): dominant allele count = (320 × 2) + 480 = 1,120, giving p = 1,120 ÷ 2,000 = 56%. Recessive count = (200 × 2) + 480 = 880, giving q = 880 ÷ 2,000 = 44% — and 56% + 44% = 100%, confirming the calculation.
A Punnett square predicts the genotype outcomes of one specific cross between two known parents, while allele frequency describes the composition of an entire existing population. Try the [Punnett Square Calculator](/punnett-square-calculator/) for individual cross predictions.
Yes — allele frequencies shift due to natural selection, genetic drift, migration (gene flow), mutation, and non-random mating. Tracking allele frequency changes across generations is one of the fundamental ways population geneticists detect and measure evolution in action.
A mismatch between observed genotype frequencies and Hardy-Weinberg predictions (calculated from your p and q) suggests the population is not at equilibrium — possibly due to selection pressure, non-random mating, small population size (genetic drift), or migration introducing new alleles.
Also known as
allele frequency formula calculatorp and q allele calculatorgene frequency calculatorgenotype count to allele frequency