Biology
Dihybrid Cross Calculator
Predict offspring ratios for a two-gene cross, assuming the genes assort independently.
Your inputs
Change any value to update the result instantly.
All-dominant phenotype probability
56.25 %
Genotype AaBb
25 %
Genotype AABb
12.5 %
Genotype AaBB
12.5 %
Genotype Aabb
12.5 %
Genotype aaBb
12.5 %
Each box of the Punnett square is equally likely; percentages are expected proportions across many offspring, not a guarantee for any single child. Assumes complete dominance and independent assortment of the genes.
What this calculator does
Predicts offspring ratios for a two-gene Mendelian cross.
What your result means
For AaBb × AaBb the phenotype split is the classic 9:3:3:1; other genotype pairs shift the split.
Formula and working
Gametes combine one allele per gene from each parent; the 4 × 4 square gives the classic 9:3:3:1 ratio for AaBb × AaBb
- 1
Collect the inputs
Parent 1 — gene A = 1; Parent 1 — gene B = 1; Parent 2 — gene A = 1; Parent 2 — gene B = 1
- 2
Apply the formula
Gametes combine one allele per gene from each parent; the 4 × 4 square gives the classic 9:3:3:1 ratio for AaBb × AaBb
- 3
Result
All-dominant phenotype probability = 56.25 %
Frequently asked questions
Symbols and assumptions
- A/a
- Alleles of gene A
- B/b
- Alleles of gene B
- • The two genes assort independently (unlinked).
- • Complete dominance at both loci.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Linked genes, epistasis and incomplete dominance are not modelled.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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