Biology
Punnett Square Calculator (Monohybrid Cross)
Predict offspring genotype and phenotype ratios for a single-gene cross between any two genotypes.
Your inputs
Change any value to update the result instantly.
All-dominant phenotype probability
75 %
Genotype Aa
50 %
Genotype AA
25 %
Genotype aa
25 %
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 Mendelian offspring genotype and phenotype probabilities for a single-gene cross.
What your result means
Percentages are expected proportions across many offspring — each child is an independent draw.
Formula and working
Each parent contributes one allele per gamete; the 2 × 2 square shows all equally likely combinations
- 1
Collect the inputs
Parent 1 genotype = 1; Parent 2 genotype = 1
- 2
Apply the formula
Each parent contributes one allele per gamete; the 2 × 2 square shows all equally likely combinations
- 3
Result
All-dominant phenotype probability = 75 %
Frequently asked questions
Symbols and assumptions
- A
- Dominant allele
- a
- Recessive allele
- • Complete dominance.
- • Unbiased segregation of alleles into gametes (Mendel's law of segregation).
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Does not model incomplete dominance, codominance, linkage or lethal genotypes.
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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