Punnett Square Calculator

Biology

Calculate genetic cross probabilities using a Punnett square. Determines offspring genotype ratios from parent alleles for single-gene inheritance patterns.

Formula

Punnett Square 2×2 grid showing all allele combinations from parent genotypes
  • A Punnett square shows 4 possible offspring combinations from two parents
  • Each parent contributes one allele (dominant A or recessive a)
  • Genotype frequencies follow Mendelian inheritance patterns
  • For Aa × Aa: 1 AA : 2 Aa : 1 aa (1:2:1 ratio)

Example

Inputs
  • Parent 1 Genotype (e.g. AA, Aa, aa): Aa
  • Parent 2 Genotype (e.g. AA, Aa, aa): Aa

Cross Aa × Aa produces: 1 AA (25%), 2 Aa (50%), 1 aa (25%).

Frequently asked questions

What is a Punnett square?
A diagram showing how alleles from two parents combine to produce offspring genotypes following Mendelian inheritance.
What do the letters mean?
Capital letter (A) = dominant allele; lowercase (a) = recessive allele. AA and aa are homozygous; Aa is heterozygous.
How do I predict phenotypes?
Dominant phenotype: AA or Aa genotypes. Recessive phenotype: only aa genotype.