Calculate the probability of brown, blue, green, hazel, or grey eyes using OCA2 and HERC2 gene models. Enter both parents and grandparents for the most accurate result.
Fill in the fields below and press Calculate. Grandparent inputs are optional but improve accuracy.
Generated at traitgen.com, Free genetics education. Not medical advice.
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⚠️ Educational only. Probability estimates based on genetic models, not medical advice.
All blue-eyed people share a single common ancestor who lived near the Black Sea around 6,000-10,000 years ago. Every blue-eyed person alive today carries the same genetic mutation from that individual.
Eye colour is primarily controlled by the OCA2 and HERC2 genes on chromosome 15. At least 16 genes contribute to the full spectrum of human eye colour, making it a polygenic trait. Brown is dominant due to higher melanin production; blue results from low melanin and Rayleigh light scattering.
OCA2 regulates melanin production in the iris. More melanin produces brown eyes; less produces blue or green. HERC2 acts as a switch that reduces OCA2 activity, explaining how two brown-eyed parents can have a blue-eyed child if both carry the recessive variant.
Brown is dominant over all other colours. Green is dominant over blue. Blue results from low melanin and light scattering. Hazel results from a combination of melanin and lipochrome pigment, sitting between brown and green on the spectrum.
A brown-eyed parent with a blue-eyed grandparent is more likely to carry the recessive blue-eye variant than one whose parents are both brown-eyed. Grandparent data helps identify these hidden carrier alleles and significantly improves prediction accuracy.
Most babies are born with blue or grey eyes as melanin production has not fully activated. Colour typically stabilises between 6 and 18 months. Final eye colour is usually set by age 3, though subtle darkening can continue until age 6 or 7.
Yes. If both parents are heterozygous carriers of the HERC2 recessive blue-eye allele, there is a 25% probability per pregnancy of a blue-eyed child. This is more common in families with Northern or Eastern European ancestry where the variant is widespread.
Most babies are born with blue or grey eyes because melanin has not fully activated. Eye colour typically stabilises between 6 and 18 months. Final colour is usually set by age 3, though subtle darkening can continue to age 6.
The calculator uses dominance hierarchy models based on OCA2 and HERC2 genetics. It provides useful estimates for brown, blue, green, hazel, and grey eyes. Because 16 or more genes contribute, actual outcomes can occasionally differ from the predicted probabilities.
No. These are educational probability estimates based on established genetic models, not clinical diagnostics. Results are for curiosity and education only. For medical genetics advice, please consult a certified genetic counsellor.