Mother’s Eye Color
Father’s Eye Color
Maternal Grandparents
Paternal Grandparents
Predicted Eye Color Probabilities
Development Timeline
Most babies are born with blue or gray eyes. Permanent color typically develops between 6 and 12 months.
Prediction Confidence
Add parent eye colors to see predictions
Eye Color Reference
How Eye Color Inheritance Works
Eye color is determined by the amount and type of melanin pigment in the iris. Brown eyes have high melanin concentration, blue eyes have very little, and colors like green, hazel, and gray fall somewhere between.
Two genes play the primary role: OCA2 and HERC2, both located on chromosome 15. HERC2 acts as a switch that controls OCA2, which in turn determines melanin production. However, at least 16 genes contribute to the final eye color, which explains why two brown-eyed parents can occasionally have a blue-eyed child.
The traditional model taught in schools (brown is dominant, blue is recessive) oversimplifies the reality. While brown alleles do tend to be dominant over lighter colors, the multi-gene inheritance pattern creates a spectrum of possible outcomes rather than strict either/or results.
Parent Combinations and Probability Ranges
Research from twin studies and large family databases provides reliable probability ranges for different parent combinations:
| Parent 1 | Parent 2 | Most Likely | Also Possible |
|---|---|---|---|
| Brown | Brown | Brown (75%) | Hazel, Green, Blue |
| Brown | Blue | Brown (50%) | Blue, Green, Hazel |
| Brown | Green | Brown (50%) | Green, Hazel, Blue |
| Blue | Blue | Blue (96%) | Gray, Green (rare) |
| Blue | Green | Blue (65%) | Green, Hazel |
| Green | Green | Green (55%) | Blue, Hazel |
| Hazel | Hazel | Hazel (45%) | Brown, Green, Blue |
| Hazel | Blue | Blue (50%) | Hazel, Green |
These probabilities shift when grandparent data is included. A brown-eyed parent with blue-eyed parents almost certainly carries a blue allele, substantially increasing the chances of passing it on.
Why Grandparent Data Improves Accuracy
Eye color genes come in pairs, one from each parent. A person with brown eyes might carry two brown alleles (homozygous) or one brown and one blue/green allele (heterozygous). Looking at a brown-eyed parent alone, you cannot tell which scenario applies.
Mother
Father
Child (25%)
If both brown-eyed parents have a blue-eyed parent, each carries a hidden blue allele. Their child has a 25% chance of inheriting both blue alleles.
Grandparents reveal hidden genetics. If a brown-eyed mother has a blue-eyed parent, she must carry at least one blue allele. This changes the probability calculations significantly. Two brown-eyed parents who each have one blue-eyed parent have approximately a 25% chance of having a blue-eyed child, much higher than the 6% baseline for brown x brown.
When Does Eye Color Become Permanent?
Most Caucasian babies are born with blue or gray eyes because melanin production in the iris has not fully developed yet. Over the first 6 to 12 months, melanocytes in the iris produce melanin in response to light exposure, gradually revealing the permanent eye color.
Timeline showing when each eye color typically stabilizes
Babies of African, Asian, or Hispanic descent are more likely to be born with brown eyes that remain brown, as higher baseline melanin levels are established before birth.
Global Distribution of Eye Colors
Eye color frequency varies dramatically by geographic ancestry due to evolutionary selection pressures:
Blue eyes are most common in Northern Europe, particularly Estonia, Finland, and Scandinavia where over 80% of the population has blue eyes. This trait evolved approximately 6,000 to 10,000 years ago from a single genetic mutation near the Black Sea region.
Green eyes are found in only 2% of the global population, with the highest concentrations in Ireland, Scotland, and parts of Northern and Central Europe.
Limitations of Eye Color Prediction
Even with complete family data, eye color prediction has inherent uncertainty:
Heterochromia: Different Colored Eyes
Some people have two different colored eyes (complete heterochromia) or multiple colors within a single iris (sectoral or central heterochromia). These conditions affect about 1% of the population and result from uneven melanin distribution during development.
Most heterochromia is genetic and harmless, passed through families without associated health issues. Acquired heterochromia developing later in life can indicate eye injury, inflammation, or other conditions and should be evaluated by an eye doctor.