🟩Punnett Square Calculator
Enter both parents' genotypes to build a monohybrid or dihybrid Punnett square, with genotype and phenotype ratios shown.
Free Punnett Square Calculator
Working through genetics and need a quick cross? Our free Punnett Square Calculator builds the full grid for you. Enter both parents' genotypes for a monohybrid cross (one gene) or a dihybrid cross (two genes), name the traits if you like, and get the complete offspring grid instantly — no manual gamete-pairing required.
Beyond the grid, you get the genotype ratio (like 1 AA : 2 Aa : 1 aa) and the phenotype ratio with percentages, using standard complete-dominance rules and your own trait labels. It handles both 2×2 monohybrid crosses and 4×4 dihybrid crosses, generating every possible gamete combination automatically so nothing gets missed.
Perfect for checking genetics homework, studying for a biology exam, or just refreshing how Mendelian inheritance works. No sign-up, no downloads — enter your genotypes and see the results immediately. See the About page or the FAQ for more.
About the Punnett Square Calculator
Features
Monohybrid & dihybrid crosses
2×2 grids for one gene, or 4×4 grids for two genes with independent assortment.
Automatic gamete generation
Every possible gamete combination is generated from each parent's genotype.
Genotype & phenotype ratios
Simplified ratios with percentages for both genotype and phenotype outcomes.
Custom trait labels
Name each gene's dominant and recessive phenotype for readable results.
Frequently Asked Questions
How does the Punnett square calculator work?
Enter both parents' genotypes, choose monohybrid or dihybrid, and it builds the full offspring grid along with genotype and phenotype ratios.
What's the difference between monohybrid and dihybrid?
Monohybrid tracks one gene (a 2×2 grid); dihybrid tracks two genes at once (a 4×4 grid) assuming independent assortment.
Can I name the traits myself?
Yes, enter your own dominant/recessive trait labels (e.g. Purple flower / White flower) and they'll appear in the phenotype ratio.
What dominance model does it use?
Simple complete dominance by default: any genotype with at least one dominant allele shows the dominant phenotype.
What if I enter an invalid genotype?
Genotypes with the wrong number of alleles or inconsistent letters are flagged immediately with a clear message.
Does it show percentages as well as ratios?
Yes, both the raw ratio (e.g. 3:1) and the percentage breakdown are shown.
Can it handle a testcross (e.g. Aa × aa)?
Yes, any valid combination of parent genotypes works, including testcrosses.
Is this tool free?
Completely free, no sign-up or downloads.
Is my data stored?
No; everything is calculated locally in your browser.
Does it work on mobile?
Yes, the grid is fully responsive and readable on small screens.