{
  "id": "baby-eye-color",
  "version": "5d6140cc12ff",
  "status": "published",
  "name": "Baby Eye Color Calculator",
  "question": "Baby eye color: what can we expect?",
  "summary": "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.",
  "category": "biology",
  "subcategory": "genetics",
  "url": "https://www.acalculator.org/biology/baby-eye-color-calculator",
  "markdown": "https://www.acalculator.org/biology/baby-eye-color-calculator.md",
  "kind": "function",
  "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."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "p1": {
        "title": "Parent 1 eye color",
        "description": "Parent 1’s eye color; pick “with a blue-eyed parent” if one of their own parents has blue eyes.",
        "type": "string",
        "enum": [
          "brown",
          "green",
          "blue",
          "brown-blue",
          "green-blue"
        ]
      },
      "p2": {
        "title": "Parent 2 eye color",
        "description": "Parent 2’s eye color; pick “with a blue-eyed parent” if one of their own parents has blue eyes.",
        "type": "string",
        "enum": [
          "brown",
          "green",
          "blue",
          "brown-blue",
          "green-blue"
        ]
      }
    }
  },
  "outputs": {
    "possible": {
      "label": "Possible eye colors",
      "description": "Every eye color the baby can have in the two-gene model.",
      "format": "text"
    },
    "brown": {
      "label": "Chance of brown eyes",
      "description": "The chance of brown eyes; a range when the parents’ genes are not known.",
      "format": "text"
    },
    "green": {
      "label": "Chance of green or hazel eyes",
      "description": "The chance of green or hazel eyes.",
      "format": "text"
    },
    "blue": {
      "label": "Chance of blue or grey eyes",
      "description": "The chance of blue or grey eyes.",
      "format": "text"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "p1": "brown",
      "p2": "blue"
    },
    "outputs": {
      "possible": "Brown, green or blue",
      "brown": "50% to 100%",
      "green": "0% to 50%",
      "blue": "0% to 50%"
    },
    "text": "Your baby’s eyes could be: Brown, green or blue."
  },
  "examples": [
    {
      "given": {
        "p1": "blue",
        "p2": "blue"
      },
      "expect": {
        "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); two bb gg parents can only pass b and g"
    },
    {
      "given": {
        "p1": "green-blue",
        "p2": "blue"
      },
      "expect": {
        "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); hand calculation in content.mdx: bb Gg × bb gg gives Gg or gg, half each"
    },
    {
      "given": {
        "p1": "brown-blue",
        "p2": "blue"
      },
      "expect": {
        "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); hand calculation in content.mdx: Bb × bb gives brown half the time; Gg × gg or gg × gg"
    },
    {
      "given": {
        "p1": "brown",
        "p2": "brown"
      },
      "expect": {
        "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); hand calculation in content.mdx: BB × anything is all brown; Bb × Bb is bb a quarter of the time"
    }
  ],
  "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)"
  ],
  "related": [
    "blood-type",
    "punnett-square",
    "hardy-weinberg"
  ],
  "changelog": []
}