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Baby Eye Color Calculator

Curious what colour your baby's eyes will be? Eye colour inheritance follows Mendelian genetics through three alleles: brown (dominant), green (intermediate), and blue (recessive). By entering each parent's eye colour, you'll see the statistical likelihood of different outcomes for your child. This tool models realistic genetic probability, accounting for homozygous and heterozygous genotypes that influence whether recessive traits—like blue eyes—emerge unexpectedly.

Last updated:

Creators Adena Benn, BSc
1,083 people find this calculator helpful

How Eye Colour Genetics Work

Eye colour is controlled by multiple genes, but the primary pattern follows a three-allele system. The brown allele is dominant over both green and blue, whilst green is dominant over blue. This means blue-eyed individuals carry only the recessive blue allele, whereas brown-eyed people may carry hidden green or blue genes.

Each parent contributes one allele to their child. Possible combinations include:

  • Homozygous: two identical alleles (e.g., BB for brown, uu for blue)
  • Heterozygous: two different alleles (e.g., Bg for brown-green, Bu for brown-blue)

A child's phenotype (visible eye colour) depends on which alleles they inherit. Because brown is dominant, even one B allele typically produces brown eyes. However, if both parents carry recessive alleles, those traits can resurface—such as two brown-eyed parents unexpectedly having a blue-eyed child.

Three-Allele Mendelian Model

The calculator uses a three-allele system where each parent's genotype is represented by two alleles. The inheritance probability for each child follows standard Mendelian genetics:

Child's allele 1 = randomly selected from Parent 1's two alleles

Child's allele 2 = randomly selected from Parent 2's two alleles

Phenotype = determined by dominance hierarchy: B > G > u

  • B — Brown allele (dominant)
  • G — Green allele (intermediate dominance)
  • u — Blue allele (recessive)
  • Phenotype — Observable eye colour, determined by allele combination

Predicting Your Baby's Eye Colour

Using the calculator is straightforward. Select the father's eye colour from the dropdown menu, then the mother's. The tool automatically generates the probability distribution for the child's potential eye colours based on all possible genotype combinations.

The results show percentages for brown, green, and blue eyes. Keep in mind these are statistical probabilities, not guarantees. In real scenarios, a single child has one outcome, but across many children or populations, the probabilities average out.

If both parents share the same eye colour, the child is more likely (but not certain) to inherit that colour. Mixed parental colours introduce more variation and recessive traits may become visible.

Important Caveats About Eye Colour Prediction

Eye colour inheritance involves genetic complexity that makes individual predictions approximate. Consider these practical limitations:

  1. Pigmentation develops slowly — Newborns often have grey, blue-grey, or lighter eyes at birth. True eye colour emerges over weeks to months as melanin deposits accumulate. Don't rely on appearance at birth; final colour may differ significantly from initial observation.
  2. Multiple genes are involved — The three-allele model simplifies a multifactorial trait. Other genes also contribute to eye colour shade and pattern. This calculator uses a dominant mathematical model but cannot account for all genetic variants that influence hazel, amber, or heterochromatic eyes.
  3. Parental genotypes are unknown — The calculator assumes a random distribution of homozygous and heterozygous combinations for each parental eye colour. If family history includes unexpected eye colours, hidden recessive genes may be more common than the model assumes, changing actual probabilities.
  4. Rare colours and patterns are excluded — Hazel, amber, and grey eyes result from complex polygenic inheritance and aren't represented here. The model covers three distinct phenotypes, so it cannot predict intermediate or unusual eye colours that fall outside this framework.

Why Can Two Brown-Eyed Parents Have a Blue-Eyed Child?

This surprises many parents, but it's entirely consistent with Mendelian genetics. A brown-eyed parent may carry the genotype Bb (brown allele + blue allele) or Bu (brown + blue). If both parents have this hidden recessive composition and each passes their blue allele to the child, the child inherits uu—blue eyes.

The probability of this event is modest (typically 6–7% when both parents are brown-eyed and carry recessive blue genes) but not negligible. Similarly, two brown-eyed parents can have green-eyed children if both carry hidden green alleles. The parent's visible phenotype does not reveal their complete genotype, which is why unexpected eye colours emerge across generations.

Frequently Asked Questions

If both parents have blue eyes, what colour will the baby's eyes be?

Two blue-eyed parents almost certainly have blue-eyed children. Since blue eyes require the homozygous recessive genotype (uu), each parent can only pass blue alleles. Their child receives one blue allele from each parent, resulting in uu and blue eyes. The probability of any other outcome is negligible unless there's a rare genetic anomaly or non-paternity.

Can a brown-eyed parent and a blue-eyed parent have a green-eyed baby?

Yes, but only if the brown-eyed parent carries a hidden green allele. For example, a parent with genotype Bg (brown-green) paired with a blue-eyed parent (uu) can produce a Gu child with green eyes. This requires the brown-eyed parent to be heterozygous for green, which is less common than carrying blue, so green outcomes are less frequent than brown or blue.

When does a baby's permanent eye colour become visible?

Newborns frequently display slate-grey or blue-grey eyes due to minimal melanin at birth. Over the first 3–12 months, melanin accumulates in the iris, and true eye colour emerges. By 6–12 months, most children show their final eye colour, though some variations can occur up to age 3. Premature infants may take longer for pigmentation to fully develop.

If I'm green-eyed and my partner is brown-eyed, what are the chances our baby has blue eyes?

The probability depends on both parents' genotypes. A green-eyed parent is typically Gg or Gu. A brown-eyed parent could be BB, Bg, Bu, or even Bg. Only specific combinations produce blue-eyed children—for instance, if the brown-eyed parent is Bu and the green-eyed parent is Gu, there's a 25% chance of uu (blue eyes). Use the calculator by entering both eye colours to see exact probabilities.

Is eye colour determined entirely by parents' eye colours?

Whilst parental eye colour is the primary determinant, the full picture is more complex. Multiple genes influence eye colour, and the three-allele model used here is a simplification. Additionally, factors like light exposure during development and individual genetic variation can subtly affect pigmentation. The calculator provides a reliable estimate based on visible parental phenotypes but cannot account for rare variants or multi-gene interactions.

My parents are both brown-eyed, but I'm blue-eyed. Is that possible?

Absolutely. Both your parents likely carry hidden recessive blue alleles—their genotypes were probably Bu or Bb (with a hidden blue gene elsewhere). If each parent passed their recessive blue allele to you, you inherited uu and express blue eyes despite their brown appearance. This isn't unusual; it simply means recessive traits from both sides aligned in your case.

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