Dihybrid Cross Calculator
BiologyBuild a 16-square dihybrid cross for two genes (AaBb x AaBb) and get the classic 9:3:3:1 phenotype ratio with a full genotype breakdown instantly.
Reviewed by the thecalcu.com team · Last updated July 21, 2026
Phenotype Ratio
What is a Dihybrid Cross?
The Dihybrid Cross Calculator builds a full 16-square cross grid for two genes inherited independently, based on each parent's genotype for both genes. Select each parent's genotype (AA/Aa/aa for gene A, BB/Bb/bb for gene B), and the calculator instantly generates all 16 offspring genotype combinations along with the resulting phenotype ratio.
For the classic AaBb × AaBb cross, this produces the famous 9:3:3:1 ratio first described by Gregor Mendel. For single-gene crosses, see the Punnett Square Calculator.
Why Use a Dihybrid Cross Calculator?
Manually building a 16-square dihybrid grid by hand is tedious and error-prone, each parent's 4 gamete combinations must be correctly derived and crossed against the other parent's 4 gametes, then each of the 16 resulting genotypes must be classified into one of four phenotype categories.
This calculator automates the entire process: gamete generation, the 16-cell grid, genotype normalization, and phenotype ratio reduction, instantly, for any combination of parent genotypes, not just the classic double-heterozygous cross.
Who Should Use This Calculator?
Biology students working through Mendelian genetics problem sets involving two-gene inheritance.
Teachers building visual demonstrations of independent assortment and the 9:3:3:1 ratio.
Genetics tutors checking student answers on dihybrid cross homework quickly and accurately.
Anyone curious about how two traits combine in offspring, from classic pea-plant examples to general genetics education.
What Insights Does This Calculator Give You?
The phenotype ratio, the primary result, reduced to its simplest integer form (like 9:3:3:1), showing the proportion of offspring expected in each phenotype category.
The full 16-square grid, every possible genotype combination, color-coded by phenotype category, so you can see exactly how each offspring genotype was derived.
Phenotype category percentages, the exact percentage of offspring expected to show each dominant/recessive combination, useful for probability-style exam questions.
How to use this Dihybrid Cross calculator
Select Parent 1's genotype for Gene A and Gene B, choose AA, Aa, or aa for gene A, and BB, Bb, or bb for gene B.
Select Parent 2's genotype for Gene A and Gene B, same options, independently for the second parent.
Read the 16-square grid, each cell shows the combined genotype (e.g., AaBb) for that offspring combination, color-coded by phenotype category.
Check the phenotype ratio, the highlighted result shows the reduced ratio (e.g., 9:3:3:1) along with the percentage breakdown for each of the four phenotype categories.
Show formula & methodology ↓Show less ↑
Formula & Methodology
Dihybrid cross process: 1. Each parent's genotype for gene A and gene B produces 4 gametes (every combination of one allele from each gene) 2. Crossing parent 1's 4 gametes against parent 2's 4 gametes produces 16 equally likely offspring combinations 3. Each offspring's genotype for gene A and gene B is normalized (dominant allele listed first) 4. Each offspring is classified as dominant or recessive for each gene, then grouped into one of 4 phenotype categories 5. Category counts are reduced to their simplest integer ratio using the greatest common divisor Classic worked example (AaBb × AaBb): Parent 1 gametes: AB, Ab, aB, ab Parent 2 gametes: AB, Ab, aB, ab Resulting 16-cell grid produces: 9 dominant/dominant, 3 dominant/recessive, 3 recessive/dominant, 1 recessive/recessive Ratio: 9 : 3 : 3 : 1 Note: This model assumes the two genes assort independently (different chromosomes, or far apart on the same chromosome) and that dominance is complete for both genes. Linked genes, incomplete dominance, or codominance would require a different calculation.
Frequently Asked Questions