Dihybrid Cross Punnett Square Calculator
Generate the full 4×4 Punnett square for two genes, see every offspring genotype, and get the phenotype ratio — choose homozygous or heterozygous parents for each gene.
Parent 1 — Gene 1 genotype
Parent 1 — Gene 2 genotype
Parent 2 — Gene 1 genotype
Parent 2 — Gene 2 genotype
| AB | Ab | aB | ab | |
|---|---|---|---|---|
| AB | AABB | AABb | AaBB | AaBb |
| Ab | AABb | AAbb | AaBb | Aabb |
| aB | AaBB | AaBb | aaBB | aaBb |
| ab | AaBb | Aabb | aaBb | aabb |
How does this calculator work?
A dihybrid cross uses a 4×4 Punnett square to show all 16 equally likely offspring when two genes are tracked simultaneously. For AaBb × AaBb the phenotype ratio is 9:3:3:1 (both dominant : first dominant only : second dominant only : double recessive). Select any combination of homozygous or heterozygous parents to see how the ratio changes.
Formula
How this is calculated
A dihybrid cross tracks the inheritance of two genes simultaneously. Each diploid parent carries two alleles for each gene; during meiosis these segregate independently (Mendel's Law of Independent Assortment) to form haploid gametes that each carry one allele per gene. For a parent heterozygous at both loci (AaBb) the four gametes are AB, Ab, aB and ab in equal frequency. Two such parents crossed together produce a 4×4 Punnett square with 16 equally likely offspring combinations.
The resulting phenotype ratio for two heterozygous parents (AaBb × AaBb) is the classic 9:3:3:1 — nine offspring express both dominant traits, three express only the first dominant, three only the second, and one is double-recessive. If either parent is homozygous at one or both loci, some gamete types collapse and the ratio changes (for example, AABb × AaBb gives 6:2:6:2 rather than 9:3:3:1).
The calculator assumes complete dominance at both loci, independent assortment (genes on different chromosomes or far apart on the same chromosome), and no lethality of any genotype. Incomplete dominance, codominance, linkage, or epistasis would alter both the grid and the ratios.
Frequently asked questions
When both parents are heterozygous for two independently assorting genes (AaBb × AaBb), the 16-cell Punnett square shows 9 offspring with both dominant phenotypes, 3 with only the first dominant, 3 with only the second, and 1 double-recessive. This 9:3:3:1 ratio was a key experimental result confirming Mendel's Law of Independent Assortment.
Homozygous parents can only produce one gamete type for that gene, so the Punnett square collapses for that dimension. A cross AABb × AaBb, for example, eliminates the aa offspring class entirely and changes the ratios. This calculator handles any combination of AA, Aa, and aa for each parent and gene.
The dihybrid Punnett square applies to any two Mendelian traits that assort independently. Human examples include blood type combined with Rh factor, or two autosomal recessive disorders on different chromosomes. More complex traits with multiple alleles, polygenic inheritance, or X-linkage require different methods.
Also known as
TG we-Calculate Editorial Team. (2026). Dihybrid Cross Punnett Square Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/dihybrid-cross-punnett-square-calculator
TG we-Calculate Editorial Team. "Dihybrid Cross Punnett Square Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/dihybrid-cross-punnett-square-calculator.
TG we-Calculate Editorial Team, "Dihybrid Cross Punnett Square Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/dihybrid-cross-punnett-square-calculator
@misc{wecalculate_dihybrid_cross_punnett_square_calculator, title = {Dihybrid Cross Punnett Square Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/dihybrid-cross-punnett-square-calculator}}, year = {2026}, note = {TG we-Calculate} }
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