Punnett Square Generator (Simple + Advanced)
Build Punnett squares for single-gene and dihybrid crosses, with clear genotype and phenotype ratios. This tool is designed for learning and includes an optional step-by-step explanation plus exports for PNG, CSV, and JSON.
Parents and mode
This is a simplified Mendelian model for learning. Real traits are often more complex.
Punnett square snapshot
Punnett Square Generator
Mode: single • Parents: Rr × Rr
| Gametes | r | R |
|---|---|---|
| r | rr | Rr |
| R | Rr | RR |
Genotype outcomes
Phenotype outcomes (simplified)
Steps
- 1) Parse parent genotypes: P1 = Rr, P2 = Rr.
- 2) Derive possible gametes: P1 → r, R; P2 → r, R.
- 3) Fill the Punnett square by combining one gamete from each parent in every cell.
- 4) Count genotypes and map each genotype to a simplified phenotype using dominance (uppercase = dominant allele).
Educational tool only. Phenotype mapping uses a simple dominance rule and does not model real-world genetic complexity.
What is a Punnett square?
A Punnett square is a simple grid-based method used in genetics to predict the distribution of offspring genotypes from two parent genotypes. You list one parent’s possible gametes across the top, the other parent’s possible gametes down the side, and then fill in each grid cell by combining alleles.
Single-gene crosses vs dihybrid crosses
A single-gene Punnett square tracks one gene with two alleles (for example, A and a). A dihybrid square tracks two genes at the same time (for example, AaBb). Dihybrid squares are larger because there are more possible gamete combinations.
Genotype ratios and phenotype ratios
The genotype ratio counts the exact allele combinations (like AA, Aa, aa). The phenotype ratio groups genotypes into observable categories. This tool uses a simplified dominance model where an uppercase allele is treated as dominant.
Important disclaimer (real traits are complex)
Many real traits are not governed by a single dominant/recessive gene pair. Traits can be polygenic, influenced by environment, show incomplete dominance, codominance, linkage, epistasis, and many other effects. Use this Punnett square generator for educational practice and conceptual understanding, not medical or predictive decision-making.
This tool runs entirely in your browser and stores your last-used settings in localStorage for convenience (clearing your browser data removes that history).