Hardy-Weinberg Equilibrium Calculator

Hardy-Weinberg Frequency and Chi-Square Test

Input Fields

Homozygous dominant

CH

Number of individuals with dominant homozygous genotype (AA)

Heterozygous

H

Number of heterozygous individuals (Aa)

Homozygous recessive

RH

Number of individuals with recessive homozygous genotype (aa)

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Your Results

Allele frequency p

Allele frequency q

Expected CH (AA)

Expected H (Aa)

Expected RH (aa)

Chi-squared (χ²)

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Hardy-Weinberg Equilibrium and Chi-Square Formula

$$p = \frac{CH + 0.5 \cdot H}{CH + H + RH} \\[5pt] q = \frac{RH + 0.5 \cdot H}{CH + H + RH} \\[10pt] E_{CH} = p^2 \cdot N \\ E_H = 2pq \cdot N \\ E_{RH} = q^2 \cdot N \\[10pt] \chi^2 = \frac{(CH – E_{CH})^2}{E_{CH}} + \frac{(H – E_H)^2}{E_H} + \frac{(RH – E_{RH})^2}{E_{RH}}$$

Where:

• $$CH$$ = number of homozygous dominant individuals
• $$H$$ = number of heterozygous individuals
• $$RH$$ = number of homozygous recessive individuals
• $$N$$ = total individuals = CH + H + RH
• $$p$$, $$q$$ = allele frequencies
• $$E_{CH}$$, $$E_H$$, $$E_{RH}$$ = expected genotype counts
• $$\chi^2$$ = chi-square value for deviation from equilibrium

The Hardy-Weinberg principle predicts genotype frequencies in a population under ideal conditions (no mutation, migration, selection, or genetic drift). This calculator allows you to input observed counts of dominant, heterozygous, and recessive individuals to determine allele frequencies (p and q), expected genotype frequencies, and whether the population deviates from equilibrium using a chi-square test. It is useful in population genetics, evolutionary biology, and academic research.