Population Genetics Calculator

Calculator input

Enter observed genotypes and evolutionary parameters

Population label

Use any name for your sample or study group.

Observed AA count

Count of homozygous dominant individuals.

Observed Aa count

Count of heterozygous individuals.

Observed aa count

Count of homozygous recessive individuals.

Fitness wAA

Relative fitness for AA, usually between 0 and 1.

Fitness wAa

Relative fitness for Aa under selection.

Fitness waa

Relative fitness for aa.

Mutation rate u (A→a)

Fraction of allele A mutating to a.

Mutation rate v (a→A)

Fraction of allele a mutating to A.

Migration rate m

Proportion of migrants entering the population.

Migrant allele A frequency

Allele A frequency among migrants.

Decimal precision

Choose displayed decimal places for the report.

Reset

Example data table

Worked example

Population	AA	Aa	aa	p(A)	q(a)	Expected Aa	Chi-square
Example Meadow Group	48	36	16	0.660000	0.340000	44.880000	3.078531
Example Forest Group	25	50	25	0.500000	0.500000	50.000000	0.000000

Formula used

Population genetics equations

Allele frequencies

p(A) = (2AA + Aa) / 2N and q(a) = 1 − p.

Observed genotype frequencies

f(AA) = AA / N, f(Aa) = Aa / N, and f(aa) = aa / N.

Hardy-Weinberg expectations

Expected AA = p²N, Expected Aa = 2pqN, and Expected aa = q²N.

Chi-square equilibrium test

χ² = Σ((Observed − Expected)² / Expected). The calculator compares χ² with the common 3.841 benchmark for one degree of freedom.

Heterozygosity and inbreeding

Ho = f(Aa), He = 2pq, and FIS = 1 − Ho / He.

Selection, mutation, and migration projection

p′selection = (p²wAA + pqwAa) / w̄, p′mutation = p′selection(1 − u) + (1 − p′selection)v, and p′next = (1 − m)p′mutation + mp_m.

How to use this calculator

Steps for accurate results

Enter the observed counts for AA, Aa, and aa from your sample.
Add relative fitness values when you want a selection-based next-generation estimate.
Enter mutation rates and migration assumptions only when your study design requires them.
Choose the display precision that fits your report or classroom needs.
Press the calculate button to place the results directly below the header.
Review allele frequencies, equilibrium metrics, and projected next-generation frequencies.
Download the report as CSV for spreadsheets or PDF for sharing.

FAQs

Frequently asked questions

1. What does this calculator measure?

It estimates genotype frequencies, allele frequencies, expected Hardy-Weinberg counts, heterozygosity, inbreeding, and a projected next-generation allele frequency using optional selection, mutation, and migration inputs.

2. When should I use observed genotype counts?

Use observed counts when you sampled individuals directly and classified them into AA, Aa, and aa groups. The calculator converts those counts into population-level summary statistics.

3. What does p(A) mean?

p(A) is the frequency of allele A in the population. Because the model is biallelic, q(a) equals one minus p(A).

4. Why is Hardy-Weinberg testing useful?

It helps you compare observed genotype counts with expected counts under random mating. Large deviations may suggest selection, population structure, inbreeding, or sampling issues.

5. What does FIS tell me?

FIS compares observed and expected heterozygosity. Positive values often indicate a heterozygote deficit, while negative values suggest a heterozygote excess.

6. Are the next-generation results exact predictions?

No. They are deterministic projections based on your fitness, mutation, and migration assumptions. Real populations may differ because of drift, sampling error, and changing environments.

7. Can I leave fitness, mutation, and migration values unchanged?

Yes. Keeping fitness at one and other rates at zero gives a baseline view focused on allele frequencies and Hardy-Weinberg structure without extra evolutionary forces.

8. Is this calculator suitable for multiallelic loci?

This version is designed for one locus with two alleles. Multiallelic systems need extended formulas and more genotype classes.