What genotypes can I enter?

For monohybrid, enter two letters for the same gene (e.g., AA, Aa, aa). For dihybrid, enter four letters representing two genes (e.g., AaBb, aaBB). Uppercase denotes the dominant allele; lowercase denotes the recessive allele.

How are gametes generated?

For each gene, homozygous parents contribute a single allele with 100% probability, while heterozygous parents contribute each allele at 50%. Gametes across genes are formed by combining one allele from each gene.

Can it do dihybrid crosses?

Yes. Select Dihybrid and enter genotypes like AaBb × AaBb. The tool generates a 4×4 grid and computes 16 offspring combinations with genotype and phenotype ratios.

How are phenotype ratios calculated?

For each gene, any genotype containing at least one uppercase allele expresses the dominant phenotype. The tool combines gene-level phenotypes to produce overall phenotype probabilities.

Does this handle non-Mendelian inheritance?

This version models simple Mendelian inheritance with complete dominance and independent assortment. Incomplete dominance, codominance, linkage, and epistasis are not modeled.

Can I share my configuration?

Yes. The Share link button copies a URL with your selected type and parental genotypes embedded as query parameters.

Punnett Square Calculator

This professional-grade Punnett square calculator helps students, educators, and biology enthusiasts quickly compute genotype and phenotype probabilities for Mendelian crosses. It supports monohybrid and dihybrid crosses, generates gametes automatically, renders the Punnett grid, and summarizes results in accessible formats.

Interactive Calculator

Monohybrid (1 gene)

Dihybrid (2 genes)

Parent 1 genotype *

Parent 2 genotype *

Results

Cross type

Monohybrid

Unique genotypes

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Unique phenotypes

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Summary

Punnett Grid

Data Source and Methodology

Authoritative Data Source: OpenStax Biology 2e — Chapter 12: Mendel’s Experiments and Heredity (2018). Direct link. All calculations are strictly based on Mendelian inheritance rules (segregation and independent assortment) as described in this source.

Scope This calculator models complete dominance and independent assortment for one or two genes. It does not account for linkage, incomplete dominance, codominance, or epistasis.

Important: All calculations are strictly based on the formulas and data provided by this source.

The Formula Explained

$$\textbf{Gamete probabilities per gene:}\quad P(\text{allele }X)=\begin{cases} 1 & \text{if homozygous }(XX \text{ or } xx)\\ \tfrac{1}{2} & \text{if heterozygous }(Xx \text{ or } xX) \end{cases}$$ $$\textbf{Offspring genotype probability (one gene):}\quad P(G)=\sum_{g_1\in \mathcal{G}_1}\sum_{g_2\in \mathcal{G}_2} \mathbf{1}[\mathrm{combine}(g_1,g_2)=G]\; P(g_1)\,P(g_2)$$ $$\textbf{Independence across genes (dihybrid):}\quad P(G_{AB})=P(G_A)\cdot P(G_B)$$ $$\textbf{Phenotype rule (complete dominance):}\quad \text{Dominant phenotype if genotype contains at least one uppercase allele; otherwise recessive.}$$

Glossary of Variables

Esempio Pratico Svolto

How it works: A step-by-step example

Select Monohybrid.
Enter Parent 1: Aa; Parent 2: Aa.
Gametes: Each parent produces A (50%) and a (50%).
Grid cells: AA, Aa, aA, aa. Canonical genotypes: AA, Aa, Aa, aa.
Using the formula:
AA = 0.5 × 0.5 = 0.25
Aa = 0.5 × 0.5 + 0.5 × 0.5 = 0.5
aa = 0.5 × 0.5 = 0.25
Phenotypes (complete dominance): A_ (dominant) = 0.75; aa (recessive) = 0.25.

Frequently Asked Questions (FAQ)

What inputs are required?

Choose Monohybrid or Dihybrid, then enter genotypes for both parents using letters only. Two letters for monohybrid (e.g., Aa) and four letters for dihybrid (e.g., AaBb).

Can I use any letters for genes?

Yes. You can use any alphabetic letters. The calculator groups alleles by their letter, ignoring case, and orders genes alphabetically for output consistency.

How does the tool handle allele order like aA vs Aa?

Order does not matter. Internally, genotypes are canonicalized with uppercase before lowercase (e.g., Aa), ensuring consistent summaries and ratios.

Why might my dihybrid ratios differ from 9:3:3:1?

Classic 9:3:3:1 ratios assume both parents are heterozygous for both genes (AaBb × AaBb) with independent assortment. If parents are not both heterozygous, or alleles are not independent, the ratio changes.

Does this support sex-linked traits?

Not in this version. The calculator focuses on autosomal genes with complete dominance. Future updates may add X-linked modeling.

How precise are the percentages?

All computations are exact rational combinations of gamete probabilities. Values are displayed to one decimal place for readability and can be shown as fractions.

Can I export the grid?

You can copy results or print the page. A CSV export option will be added in a future release.

Tool developed by Ugo Candido.
Content verified by CalcDomain Editorial Team.
Last reviewed for accuracy on: September 15, 2025.