What is the Genetic Probability Calculator?
Calculate Mendelian inheritance probabilities with an interactive Punnett square. Enter parent genotypes for monohybrid (Aa × Aa) or dihybrid (AaBb × AaBb) crosses and get genotype and phenotype percentages instantly. Uppercase alleles are treated as dominant. Free, private, and runs in your browser.
How to use the Genetic Probability Calculator
- Choose Auto-detect, Monohybrid, or Dihybrid cross type.
- Enter Parent 1 and Parent 2 genotypes (e.g. Aa or YyRr).
- Review the Punnett square with all offspring genotypes.
- Read genotype and phenotype probability tables.
- Copy the summary for biology homework or lesson plans.
Common use cases
- Finding the probability of recessive offspring from two heterozygotes
- Solving dihybrid cross ratios for biology class
- Checking expected phenotype ratios for a Mendelian genetics problem
Frequently asked questions
- What is a Punnett square?
- A Punnett square is a grid that combines gametes from two parents to predict offspring genotype ratios. Each cell represents one equally likely offspring combination.
- How are dominant and recessive alleles determined?
- Uppercase letters are treated as dominant (e.g. A in Aa) and lowercase as recessive (a). Homozygous dominant (AA) and heterozygous (Aa) both show the dominant phenotype.
- What is a dihybrid cross?
- A dihybrid cross tracks two genes at once, such as AaBb × AaBb. The tool assumes genes assort independently (Mendel's law of independent assortment).
- Why do probabilities not always add to exactly 100%?
- Percentages are rounded to one decimal place. The underlying counts always sum to the total number of Punnett square cells.
- Is my data uploaded?
- No. All calculations run locally in your browser.
