Eye Color Punnett Square Calculator
Educational model using two genes: B/b (brown influence) and G/g (green influence). Real eye color genetics are more complex.
- B = dominant brown allele, b = recessive brown allele
- G = dominant green allele, g = recessive green allele
- Predicted phenotype rules used here: B_ + G_ = Hazel/Brown, B_ + gg = Brown, bb + G_ = Green, bbgg = Blue
What this eye color Punnett square calculator does
This calculator estimates possible child eye color outcomes from two parent genotypes using a simplified two-gene model. It creates a full Punnett square, counts each genotype combination, and converts those genotype counts into phenotype probabilities.
If you are learning genetics in school, this is useful for visualizing inheritance patterns. If you are a parent or just curious, it gives an approachable estimate based on dominant and recessive allele behavior.
How to read the genotype notation
The first pair: B or b
The first two letters represent the brown-color influence locus. Any genotype with at least one uppercase B has the dominant brown effect. Only bb lacks it.
The second pair: G or g
The second two letters represent a green-color influence locus in this model. Any genotype with at least one uppercase G has the dominant green effect. Only gg lacks it.
Phenotype mapping used in this calculator
- B_ and G_ → Hazel/Brown
- B_ and gg → Brown
- bb and G_ → Green
- bb and gg → Blue
How the calculation works
Each parent contributes one allele from each gene to a child. For two genes, each parent has four possible gamete combinations. The calculator forms a 4×4 Punnett square (16 outcomes total), then counts repeating results to generate percentages.
For example, if both parents are BbGg, each can pass BG, Bg, bG, or bg. Combining these gives the full range of predicted offspring genotypes and phenotypes.
Important realism note
Human eye color is polygenic and influenced by multiple genes beyond two loci. Environmental and developmental factors can also affect final appearance. So this tool is best for classroom-style Mendelian practice and quick inheritance intuition, not clinical prediction.
Tips for getting better genetics intuition
- Try crossing bbgg × bbgg to see why blue can be strongly recessive in this model.
- Try BbGg × bbgg to understand test-cross style distributions.
- Compare BBgg × bbGG to observe how all children can share one phenotype despite different allele origins.
- Look at genotype percentages and phenotype percentages separately—they are not always the same.
Quick FAQ
Can two brown-eyed parents have a blue-eyed child?
In simplified models, yes—if both parents carry recessive alleles and the child inherits recessive combinations (such as bbgg in this two-gene setup).
Why do I see many genotypes but fewer phenotypes?
Because different genotypes can map to the same visible eye-color category. Dominant alleles often collapse multiple genotype combinations into one phenotype.
Is this medically diagnostic?
No. This is an educational eye color inheritance calculator intended for biology learning and estimation only.