Punnett Square Calculator

Calculate Mendelian inheritance outcomes with a Punnett square. Supports monohybrid, dihybrid (two-trait), and X-linked sex-linked crosses. Includes phenotype ratios and chi-square test.

% AA (Homozygous Dominant)
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% Aa (Heterozygous) —
% aa (Homozygous Recessive) —
Phenotype Ratio (Dom:Rec) —
Extended More scenarios, charts & detailed breakdown ▾
% AA
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% Aa —
% aa —
Phenotype Ratio —
Professional Full parameters & maximum detail ▾
Phenotype Description
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% AA —
% Aa —
% aa —
Chi-Square vs 3:1 (for Aa × Aa) —

How to Use This Calculator

  1. Select Parent 1 and Parent 2 genotypes (AA, Aa, or aa).
  2. Results show offspring genotype percentages and dominant-to-recessive phenotype ratio.
  3. Use Two Traits for dihybrid crosses (AaBb format).
  4. Use Sex-Linked for X-linked inheritance with mother/father genotypes.

Formula

Monohybrid cross: Aa × Aa → 1 AA : 2 Aa : 1 aa (genotype) → 3 dominant : 1 recessive (phenotype)

Dihybrid cross: AaBb × AaBb → 9 A_B_ : 3 A_bb : 3 aaB_ : 1 aabb

Example

Example: Aa × Aa: offspring are 25% AA, 50% Aa, 25% aa. Phenotype: 75% dominant (AA + Aa) : 25% recessive (aa) = 3:1 ratio.

Frequently Asked Questions

  • A Punnett square is a grid used to predict the probability of offspring genotypes from a genetic cross. Each row represents a gamete from one parent; each column from the other. The cells show possible offspring genotypes.
  • Crossing two heterozygous parents (Aa × Aa) produces AA (25%), Aa (50%), aa (25%). Since A is dominant, 75% show the dominant phenotype and 25% show the recessive phenotype — a 3:1 phenotype ratio.
  • A dihybrid cross involves two independent traits simultaneously (e.g., AaBb × AaBb). Following the Law of Independent Assortment, the expected phenotype ratio is 9:3:3:1 (both dominant : first dominant only : second dominant only : both recessive).
  • In incomplete dominance, heterozygotes show an intermediate phenotype — neither fully dominant nor fully recessive. Example: red (RR) × white (rr) → pink (Rr) flowers in snapdragons. The phenotype ratio is 1:2:1 rather than 3:1.
  • X-linked traits are carried on the X chromosome. Males (XY) only have one copy, so they express the trait if they carry even one recessive allele. Females need two recessive alleles (X^a X^a) to express X-linked recessive traits. This is why conditions like hemophilia and color blindness are more common in males.

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Sources & References (5) ▾
  1. Mendel G. (1866) — Versuche über Pflanzenhybriden (Experiments on Plant Hybridization) — Verhandlungen des naturforschenden Vereines in Brünn
  2. OpenStax Biology 2e, Chapter 12: Mendel's Experiments and Heredity — OpenStax
  3. NCBI Bookshelf — An Introduction to Genetic Analysis (Griffiths et al.) — NCBI / W.H. Freeman
  4. Khan Academy — Mendelian Genetics (AP Biology) — Khan Academy
  5. Griffiths et al. — Introduction to Genetic Analysis, 12th Ed. — Macmillan / W.H. Freeman