A baby eye color calculator using simple genetics
What colour eyes will your baby have? This baby eye color calculator gives the chance of brown, green or hazel, and blue or grey eyes from the parents’ eye colours — and, if you know them, the four grandparents’ too. It uses the two-gene model taught in many biology classes and works it out exactly, like a Punnett square that keeps track of every possibility.
It is for fun. Real eye colour is shaped by many genes, so the percentages are an entertainment estimate, not a prediction you can count on and not a genetic or medical test. Everything runs in your browser; nothing is stored or sent anywhere.
How to use the Baby Eye Color Calculator
- Choose the mother’s eye color and the father’s eye color. Hazel counts as green and grey as blue in this model.
- Optionally open Add grandparents and set any of the four grandparents you know. Leave the others on “Don’t know”.
- Read the most likely colour and the bar for each colour. The numbers update as you change any choice.
- If you see a message that a combination is impossible, that is the simple model’s limit, not a mistake in your family — clear a grandparent to continue.
Baby Eye Color Calculator features
Exact two-gene maths
Every possible combination of gene copies is counted, not a rough lookup table.
Grandparents improve it
Grandparents’ eye colours change which hidden gene copies each parent probably carries.
Hazel and grey
Both are accepted: hazel is grouped with green and grey with blue, as in the classic model.
Clear limits
Impossible combinations in the model are flagged rather than hidden.
Private
No sign-up and no upload: the calculation happens on your device.
How the two-gene model works
The model uses two genes, and each person has two copies of each, one from each parent. The brown gene (often labelled bey2, in the HERC2/OCA2 region of chromosome 15) comes in a brown and a non-brown version; one brown copy is enough for brown eyes. The green gene (often labelled gey) comes in a green and a blue version; if a person has no brown copy, one green copy gives green or hazel eyes, and two blue copies give blue eyes.
A brown-eyed parent may carry a hidden non-brown copy, and a green-eyed parent may carry a hidden blue copy. We do not know which, so the calculator starts from the assumption that both versions of each gene are equally common, works out how likely each hidden combination is, and then passes one copy of each gene from each parent to the baby at random. Grandparents’ eye colours narrow down which hidden copies are possible.
| Parents | Brown | Green / hazel | Blue / grey |
|---|---|---|---|
| Brown × brown | 88.9% | 8.3% | 2.8% |
| Brown × blue | 66.7% | 16.7% | 16.7% |
| Green × blue | 0% | 66.7% | 33.3% |
| Blue × blue | 0% | 0% | 100% |
Why real eye colour is more complicated
MedlinePlus Genetics (US National Library of Medicine) explains that two neighbouring genes on chromosome 15, OCA2 and HERC2, have the biggest effect, and at least eight more genes — including ASIP, IRF4, SLC24A4, SLC24A5, SLC45A2, TPCN2, TYR and TYRP1 — add smaller effects. That is why eye colour comes in a continuous range of shades, and why two blue-eyed parents can, uncommonly, have a brown-eyed child — something the simple model says is impossible.
How common each version of a gene is also differs between populations. In much of South Asia, Africa and East Asia almost everyone has brown eyes, so the real chance of a lighter colour there is far lower than the equal-odds starting point used here.
When does a baby’s eye colour settle?
Many babies of European ancestry are born with blue or grey eyes that darken over the first year as the iris builds up melanin; most have their lasting colour by about 1 to 3 years. Babies with darker skin are usually born with brown eyes. Eyes that change colour later in childhood, or one eye that looks different from the other, are worth mentioning to your doctor.
If you enjoy family trait guesses, the baby hair color calculator uses a similar simplified model, and the child height predictor estimates adult height from the parents’ heights.
Baby Eye Color Calculator FAQ
How accurate is a baby eye color calculator?
Only roughly. It follows a two-gene teaching model; real eye colour depends on many genes, so treat the result as a fun estimate. It is not a genetic test.
Can two brown-eyed parents have a blue-eyed baby?
Yes. If both parents carry a hidden non-brown copy, the model gives about a 1 in 9 chance of a non-brown baby when nothing else is known, and a 1 in 36 chance of blue. Grandparents with blue eyes make it more likely.
Can two blue-eyed parents have a brown-eyed baby?
In the simple model, no. In real life it is uncommon but possible, because other genes also affect eye colour.
How does the calculator handle hazel eyes?
Hazel is treated as part of the green group, and grey as part of the blue group, because the two-gene model only has three outcomes.
Do grandparents really matter?
They help: a blue-eyed grandparent means a brown-eyed parent must carry a hidden non-brown copy, which raises the chance of lighter eyes in the baby.
When will I know my baby’s eye colour?
Usually by the first birthday, although some children’s eyes keep changing a little until about age 3.