# Baby eye color: what can we expect?

Gives the eye colors a baby can have from the parents’ eye colors, with the chance of brown, green and blue eyes by the two-gene model of eye color.

- Page: https://www.acalculator.org/biology/baby-eye-color-calculator
- JSON spec: https://www.acalculator.org/biology/baby-eye-color-calculator.json
- Version: 5d6140cc12ff

## Default answer

Example with the default inputs (Parent 1 eye color Brown, Parent 2 eye color Blue or grey): Your baby’s eyes could be: Brown, green or blue.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| p1 | Parent 1 eye color | Parent 1’s eye color; pick “with a blue-eyed parent” if one of their own parents has blue eyes. |
| p2 | Parent 2 eye color | Parent 2’s eye color; pick “with a blue-eyed parent” if one of their own parents has blue eyes. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| possible | Possible eye colors | Every eye color the baby can have in the two-gene model. |
| brown | Chance of brown eyes | The chance of brown eyes; a range when the parents’ genes are not known. |
| green | Chance of green or hazel eyes | The chance of green or hazel eyes. |
| blue | Chance of blue or grey eyes | The chance of blue or grey eyes. |

## Method

Brown = at least one BEY2 brown allele; green = no brown allele and at least one GEY green allele; blue = neither. Each parent passes each allele with chance 1/2.

## Assumptions

- This is the two-gene teaching model. Eye color depends on many genes, so real children can have colors the model rules out, such as brown eyes from two blue-eyed parents.
- A parent known only by eye color may have several genotypes, so each chance is shown as the lowest to the highest over them.
- Hazel counts as green and grey as blue.

## Worked examples

1. p1 = blue, p2 = blue gives possible = Blue only, brown = 0%, green = 0%, blue = 100%. Source: The Tech Interactive, Ask a Geneticist, Which eye color alleles do I have? (Patel, 2005: in the two-gene model, a working copy of BEY2 gives brown eyes whatever GEY has; with no working BEY2, a working GEY gives green; with neither, blue), https://www.thetech.org/ask-a-geneticist/articles/2005/ask108/ (retrieved 2026-10-03).
2. p1 = green-blue, p2 = blue gives possible = Green or blue, brown = 0%, green = 50%, blue = 50%. Source: The Tech Interactive, Ask a Geneticist, Which eye color alleles do I have? (Patel, 2005: in the two-gene model, a working copy of BEY2 gives brown eyes whatever GEY has; with no working BEY2, a working GEY gives green; with neither, blue), https://www.thetech.org/ask-a-geneticist/articles/2005/ask108/ (retrieved 2026-10-03).
3. p1 = brown-blue, p2 = blue gives possible = Brown, green or blue, brown = 50%, green = 0% to 25%, blue = 25% to 50%. Source: The Tech Interactive, Ask a Geneticist, Which eye color alleles do I have? (Patel, 2005: in the two-gene model, a working copy of BEY2 gives brown eyes whatever GEY has; with no working BEY2, a working GEY gives green; with neither, blue), https://www.thetech.org/ask-a-geneticist/articles/2005/ask108/ (retrieved 2026-10-03).
4. p1 = brown, p2 = brown gives brown = 75% to 100%, green = 0% to 25%, blue = 0% to 25%. Source: The Tech Interactive, Ask a Geneticist, Which eye color alleles do I have? (Patel, 2005: in the two-gene model, a working copy of BEY2 gives brown eyes whatever GEY has; with no working BEY2, a working GEY gives green; with neither, blue), https://www.thetech.org/ask-a-geneticist/articles/2005/ask108/ (retrieved 2026-10-03).

## FAQ

### How is eye color inherited?

In the two-gene model, one gene (BEY2) has a brown and a blue allele, and brown is dominant. A second gene (GEY) has a green and a blue allele, and green is dominant over blue. Any brown allele gives brown eyes; with no brown allele, any green allele gives green; with neither, blue.

### Can two blue-eyed parents have a brown-eyed baby?

Not in the two-gene model, which gives blue eyes only. In real life it is uncommon but possible, because eye color depends on many genes. MedlinePlus Genetics notes that the old one-gene rule was too simple.

### Why does the calculator show a range like 0% to 25%?

A brown-eyed parent may carry hidden blue or green alleles, or not, and eye color alone does not tell which. The calculator works out every set of genes the parents could have and shows the lowest to the highest chance. Knowing that a parent has a blue-eyed parent narrows it.

### What does “with a blue-eyed parent” change?

A blue-eyed person passes only blue alleles. So a brown-eyed parent whose mother or father has blue eyes must carry one blue BEY2 allele (Bb), and a green-eyed parent with a blue-eyed parent must be Gg. That turns some ranges into single numbers.

### How accurate is this?

It is a teaching model, not a test. The Tech Interactive notes that at least 50 genes play a part, so a real baby can have a color the model gives as 0%. Use it for fun and to learn how dominant and recessive alleles work.

### Where do hazel and grey eyes fit?

The model has only three colors. The calculator counts hazel as green and grey as blue.

## Sources

- The Tech Interactive, Ask a Geneticist, Which eye color alleles do I have? (Patel, 28 April 2005, with a 2021 editor’s note: the two-gene BEY2 and GEY model, brown overriding green and blue; eye color involves at least 50 genes). https://www.thetech.org/ask-a-geneticist/articles/2005/ask108/ (retrieved 2026-10-03)
- MedlinePlus Genetics, Is eye color determined by genetics? (OCA2 and HERC2 on chromosome 15; eye color does not follow a simple dominant and recessive pattern; blue-eyed parents can, uncommonly, have brown-eyed children; reviewed 7 July 2022). https://medlineplus.gov/genetics/understanding/traits/eyecolor/ (retrieved 2026-10-03)