How to use the Baby Eye Color
- Select each parent's eye colour.
- Add grandparents' colours if known, since recessive alleles hide a generation.
- Read the probability spread across brown, green and blue.
- Treat the output as a probability, never a prediction.
How the calculation works
At least a dozen genes influence iris pigmentation, with OCA2 and HERC2 on chromosome 15 accounting for the majority of the variation. Brown alleles are generally dominant over green, and green over blue, which is why the classical model gets the broad strokes right. But two blue-eyed parents can occasionally have a green- or brown-eyed child, which the simple model calls impossible — the polygenic reality allows it.
Most babies of European ancestry are born with blue or grey eyes because melanin has not yet accumulated in the iris stroma. Colour typically settles between six and twelve months and can continue darkening until about age three. Babies of African and Asian ancestry are usually born with brown eyes already, since pigmentation is present from birth. Hazel and amber sit on a continuum of intermediate melanin rather than forming discrete categories.
Polygenic model: probability spread weighted by parental phenotypes and known recessive carriersSource: OCA2/HERC2 polygenic model of human iris pigmentation from population genetics studies.
Worked example
A brown-eyed parent with one blue-eyed parent of their own, and a blue-eyed partner.
- The brown-eyed parent almost certainly carries a blue allele from their own parent.
- The blue-eyed partner contributes only blue alleles.
- Roughly half the children inherit the brown allele.
- Approximate spread: 50% brown, 12% green, 38% blue.
Close to an even split between brown and blue, with a small chance of green.
Frequently asked questions
Can two blue-eyed parents have a brown-eyed child?+
Rarely, yes. The polygenic model allows it, unlike the simplified dominant-recessive version.
When does eye colour settle?+
Usually between six and twelve months, though darkening can continue to around age three.
Why are so many babies born with blue eyes?+
Melanin has not yet accumulated in the iris. It is not the final colour.
How accurate is this?+
It is a probability estimate from a simplified model. Genetics does not offer certainty here.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.