# Baby Eye Color Predictor _Pick each parent's eye color and see the odds for your baby's, with the Punnett squares behind them._ - Source: https://proba.baby/en/tools/baby-eye-color-predictor - Language: English - Last verified: v1.0.4 · 7 Sep 2026 - Last updated: 2026-10-10 ## How it works Pick each parent's eye color from brown, amber, hazel, green, gray or blue. If you know the grandparents' eye colors, open the optional section and add them. The result updates as you click, and the page address keeps your choices so you can send them to someone. The tool uses a simplified two-gene model. HERC2 works like a switch: with two "off" copies (bb) the pigment gene is shut down and the eyes are blue or gray. OCA2 makes the pigment: with the switch on, at least one working copy (P) gives brown or amber eyes, and none (pp) gives hazel or green. Two genes cannot tell the shades inside each pair apart, so the result comes in three groups. You can see a parent's eye color but not their genes. A brown-eyed parent may or may not carry a hidden "off" copy, so the tool does not guess. It keeps every set of genes that fits the eye color and weighs them, starting from even odds for each version of each gene. That makes a brown-eyed parent a hidden carrier two times in three. The grandparents' eye colors then shift those odds: a blue-eyed grandparent makes the parent a certain carrier, and brown-eyed grandparents make it less likely. Real eye color depends on dozens of genes, so treat the percentages as a way to see how inheritance works, not as a forecast. The result is an entertainment estimate, not genetic testing or medical advice. ## The math The starting point (the prior). Before anyone's eye color is known, the two versions of each gene are taken as equally common, so a person is BB, Bb or bb in the ratio 1 : 2 : 1 (and PP, Pp or pp the same). This is a deliberately neutral choice: how common the hidden variants are differs between populations, and this page does not ask about ancestry. Reading a parent's eye color. Brown or amber means HERC2 BB or Bb and OCA2 PP or Pp. Keeping the 1 : 2 : 1 weights, the parent is Bb with chance 2/3 and passes on B with chance 1/3 + 2/3 × 1/2 = 2/3; the same holds for P. Hazel or green means BB or Bb with pp (passes B with chance 2/3, never P). Blue or gray means bb (never passes B); OCA2 is hidden behind the switch, so it keeps 1 : 2 : 1 and passes P with chance 1/2. The baby. For each gene the tool builds a weighted Punnett square: each parent's two alleles are weighted by the chance that parent passes them on. The baby is blue or gray when both parents pass b; hazel or green when the switch is on but both pass p; brown or amber otherwise. For a brown-eyed and a blue-eyed parent: blue or gray = 1/3 × 1 = 1/3; both pass p = 1/3 × 1/2 = 1/6; so brown or amber = 2/3 × 5/6 = 5/9 (56%) and hazel or green = 2/3 × 1/6 = 1/9 (11%). Grandparents (updating the odds). A grandparent's eye color limits their own genes the same way, and an unknown grandparent keeps the 1 : 2 : 1 start. Crossing the two grandparents gives the parent's possible genes; the parent's own eye color then rules some out, and the rest are rescaled to add up to 1. Two brown-eyed parents who each have a blue-eyed parent are both certain carriers (Bb), so their baby is blue or gray with chance 1/2 × 1/2 = 1/4: the classic one in four. If the grandparents' colors cannot produce the parent's color in this model, the tool leaves them out and says so. Percentages are rounded to whole numbers, so a list can add up to 99 or 101. The tool shows 100% only when the model leaves no other outcome, which happens only when both parents have blue or gray eyes. The checks behind this page compare the code with eight hand-worked examples and confirm that no other pairing, with any grandparents, reaches 100%. ## FAQ **Can two brown-eyed parents have a blue-eyed baby?** Yes, if both carry a hidden light-eye variant. With no family information the tool counts each brown-eyed parent as a carrier two times in three, which gives an 11% chance of blue or gray eyes. If a blue- or gray-eyed grandparent on each side shows that both parents are carriers, the chance becomes 25%, the classic one in four. **What eye color will a baby of a brown-eyed and a blue-eyed parent have?** The tool shows 56% brown or amber, 11% hazel or green and 33% blue or gray. The blue-eyed parent always passes on the switch-off copy of HERC2, so the baby has light eyes only if the brown-eyed parent passes one on too. Brown-eyed grandparents on that side lower the light-eye chance; a blue-eyed grandparent raises it to 50%. **Why does the tool show three color groups instead of six colors?** Two genes are not enough to separate brown from amber, hazel from green, or blue from gray: those shades depend on other genes and on the structure of the iris. Rather than invent numbers, the tool reports the group and leaves the exact shade open. **Why does the tool start from even odds?** It has to start somewhere. How common the hidden variants are differs a lot between populations, and the page does not ask about ancestry, so it assumes the two versions of each gene are equally common. That is the neutral textbook starting point, and adding grandparents is the way to fit it to your family. **How accurate is a baby eye color predictor?** It is a guide, not a forecast. Large studies find that eye color involves more than 60 regions of the genome, while this tool uses two genes. A newborn's eyes can also change color during the first years. **Which genes decide eye color?** OCA2 and HERC2, next to each other on chromosome 15, account for most of the difference between blue and brown. HERC2 contains a regulatory switch that controls how active OCA2 is, and OCA2 helps make the iris pigment melanin. Several other genes fine-tune the shade. **Do grandparents change the odds?** Yes. They are clues to what each parent carries. A blue- or gray-eyed grandparent shows that a brown-eyed parent carries the switch-off copy; two brown-eyed grandparents make that less likely. The tool updates each parent's odds with these clues, as the math section below sets out. **What color will my newborn's eyes be?** The color at birth is often not the final one. Many babies begin with gray or blue-gray eyes and their color can shift as the iris makes more melanin over the first months and years. The tool predicts the inherited tendency, not the color on day one. **Is this the same as the prediction in the ProbaBaby app?** Yes, the genetic model is the same. The ProbaBaby app's prediction uses this page's two-gene model: it keeps every HERC2 and OCA2 combination a parent could carry and weighs each one, instead of guessing a single one. On top of that, the app adjusts the odds for the ancestry you enter, gives each of 6 eye colors its own odds and adds hair, skin tone, height and facial features. Premium also asks for 4 grandparents' eye and hair color and each side's family history. ## Sources - MedlinePlus Genetics (NIH): Is eye color determined by genetics? — OCA2, HERC2 and eight other contributing genes: https://medlineplus.gov/genetics/understanding/traits/eyecolor/ - Sturm RA et al. A single SNP in an evolutionary conserved region within intron 86 of the HERC2 gene determines human blue-brown eye color. Am J Hum Genet 2008 — The HERC2 regulatory switch that controls OCA2: https://pmc.ncbi.nlm.nih.gov/articles/PMC2427173/ - Simcoe M et al. Genome-wide association study in almost 195,000 individuals identifies 50 previously unidentified genetic loci for eye color. Sci Adv 2021 — 124 associations across 61 genomic regions: eye color is polygenic: https://pmc.ncbi.nlm.nih.gov/articles/PMC7946369/ --- ProbaBaby (listed on the App Store as “Pregnancy & Baby Tracker - PB”) is a free iPhone, iPad and Apple Watch app for pregnancy, newborn and postpartum tracking, built for twins, in 32 in-app languages, with an optional AI baby-face prediction that computes Mendelian genetics (Punnett squares) from the traits you enter before any image is generated. Tracking, tools, PDF reports and family sharing are free; only AI predictions use credits — 5 starter credits cover your first Scientific prediction — and no subscription is required. Requires iOS 26 or later. Not available on Android.