{
  "id": "dog-age",
  "version": "1b9af9a09c07",
  "status": "published",
  "name": "Dog Age Calculator",
  "question": "What is my dog’s age in human years?",
  "summary": "Converts a dog’s age to human years with the size-based chart vets use, and shows the 2020 DNA-method estimate for comparison.",
  "category": "days",
  "subcategory": "age",
  "url": "https://www.acalculator.org/days/dog-age-calculator",
  "markdown": "https://www.acalculator.org/days/dog-age-calculator.md",
  "kind": "function",
  "method": "Read the human age for the dog’s age and size group off the size chart, on a straight line between whole years; the DNA method is 16 ln(age) + 31.",
  "assumptions": [
    "The size group comes from the breed’s adult weight: small up to 20 lb, medium 21 to 50 lb, large 51 to 100 lb, giant over 100 lb.",
    "Between whole years, the chart is read on a straight line; year 0 counts as 0 human years, and past 16 the chart’s last yearly step repeats.",
    "Age from a birthday is days ÷ 365.2425 years; the displayed age is the calendar difference in whole years, months, and days.",
    "The DNA method comes from a study of Labrador Retrievers and is shown for comparison only; it is left out for puppies under about 7 weeks, where it would be below 0.",
    "A February 29 birthday falls on February 28 in other years."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "breed": {
        "title": "What breed?",
        "description": "The breed, which sets the size group, or a mixed-breed size by adult weight.",
        "type": "string",
        "enum": [
          "101",
          "102",
          "103",
          "104",
          "58",
          "52",
          "60",
          "81",
          "72",
          "47",
          "12",
          "85",
          "36",
          "8",
          "32",
          "22",
          "46",
          "50",
          "30",
          "89",
          "24",
          "83",
          "16",
          "78",
          "28",
          "90",
          "6",
          "56",
          "68",
          "18",
          "62",
          "14",
          "53",
          "34",
          "66",
          "94",
          "29",
          "39",
          "9",
          "49",
          "15",
          "65",
          "40",
          "26",
          "88",
          "1",
          "4",
          "10",
          "70",
          "3",
          "97",
          "19",
          "64",
          "71",
          "25",
          "76",
          "100",
          "69",
          "63",
          "92",
          "2",
          "79",
          "87",
          "74",
          "38",
          "37",
          "31",
          "73",
          "17",
          "43",
          "91",
          "86",
          "98",
          "77",
          "67",
          "96",
          "11",
          "23",
          "5",
          "45",
          "35",
          "82",
          "48",
          "7",
          "75",
          "51",
          "55",
          "54",
          "27",
          "42",
          "20",
          "21",
          "57",
          "95",
          "84",
          "80",
          "99",
          "33",
          "41",
          "44",
          "61",
          "93",
          "59",
          "13"
        ]
      },
      "known": {
        "title": "What do you know?",
        "description": "Whether you know the birthday or the age in years and months.",
        "type": "string",
        "enum": [
          "birth",
          "age"
        ]
      },
      "birth": {
        "title": "When were they born?",
        "description": "Your dog’s birthday.",
        "type": "string",
        "format": "date"
      },
      "on": {
        "title": "Age on",
        "description": "The date to work out the age on. Today, unless you change it.",
        "type": "string",
        "format": "date"
      },
      "years": {
        "title": "Years",
        "description": "Your dog’s age in whole years, when you do not give a birthday.",
        "type": "integer",
        "minimum": 0,
        "maximum": 30
      },
      "months": {
        "title": "Months",
        "description": "Months past the whole years, 0 to 11.",
        "type": "integer",
        "minimum": 0,
        "maximum": 11
      }
    }
  },
  "outputs": {
    "human": {
      "label": "In human years",
      "description": "The human-equivalent age on the size chart, read on a straight line between whole years.",
      "format": "number"
    },
    "age": {
      "label": "Age",
      "description": "Your dog’s age in years, months, and days (days only when the birthday is known).",
      "format": "duration"
    },
    "dna": {
      "label": "DNA method",
      "description": "The human-equivalent age from 16 ln(age in years) + 31 (Wang et al., 2020).",
      "format": "number"
    },
    "size": {
      "label": "Size group",
      "description": "The chart’s size group for this breed.",
      "format": "text"
    },
    "life": {
      "label": "Typical life span",
      "description": "The breed’s typical life span from the American Kennel Club.",
      "format": "text"
    },
    "next": {
      "label": "Next birthday",
      "description": "The next birthday after the age-on date, when the birthday is known.",
      "format": "date"
    },
    "days": {
      "label": "Days to next birthday",
      "description": "Days from the age-on date to the next birthday.",
      "format": "integer"
    },
    "nextHuman": {
      "label": "In human years at the next birthday",
      "description": "The size-chart age on the next birthday.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "breed": "3",
      "known": "birth",
      "birth": "2021-10-05",
      "on": "2026-10-05",
      "years": 5,
      "months": 3
    },
    "outputs": {
      "human": 35.99767277904406,
      "age": {
        "years": 5,
        "months": 0,
        "days": 0
      },
      "dna": 56.7491447138533,
      "size": "Large (51 to 100 lb)",
      "life": "10 to 12 years",
      "next": "2027-10-05",
      "days": 365,
      "nextHuman": 45
    },
    "text": "A Golden Retriever aged 5 years is about 36 in human years."
  },
  "examples": [
    {
      "given": {
        "breed": "3",
        "known": "age",
        "years": 5,
        "months": 0
      },
      "expect": {
        "human": 36,
        "dna": 56.75100659894561,
        "size": "Large (51 to 100 lb)",
        "life": "10 to 12 years"
      },
      "source": "size chart (AVMA, via The Old Farmer’s Almanac); Wang et al., 2020; hand calculation in content.mdx"
    },
    {
      "given": {
        "breed": "19",
        "known": "age",
        "years": 6,
        "months": 6
      },
      "expect": {
        "human": 52.5,
        "dna": 60.94883483042546
      },
      "source": "hand calculation in content.mdx"
    },
    {
      "given": {
        "breed": "34",
        "known": "birth",
        "birth": "2020-02-29",
        "on": "2026-09-27"
      },
      "expect": {
        "age": {
          "years": 6,
          "months": 6,
          "days": 29
        },
        "human": 42.30581052314558,
        "next": "2027-02-28",
        "days": 154,
        "nextHuman": 44
      },
      "source": "hand calculation in content.mdx"
    },
    {
      "given": {
        "breed": "3",
        "known": "birth",
        "birth": "2026-09-07",
        "on": "2026-09-28"
      },
      "expect": {
        "age": {
          "years": 0,
          "months": 0,
          "days": 21
        },
        "human": 0.8624407072013799
      },
      "source": "hand calculation in content.mdx: 21 days; 21 ÷ 365.2425 × 15 = 0.862"
    }
  ],
  "sources": [
    "The Old Farmer’s Almanac, Dog Age Chart: dog years to human years by size (after the American Veterinary Medical Association). https://www.almanac.com/dog-age-chart-dog-years-human-years",
    "American Kennel Club, How to Calculate Dog Years to Human Years. https://www.akc.org/expert-advice/health/how-to-calculate-dog-years-to-human-years/",
    "Wang T, Ma J, Hogan AN, et al. Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome. Cell Systems 11(2):176-185, 2020. https://doi.org/10.1016/j.cels.2020.06.006",
    "American Kennel Club breed pages (weights and life spans), https://www.akc.org/dog-breeds/; Fédération Cynologique Internationale standard No. 343 (Cane Corso weight); United Kennel Club Spinone Italiano standard, https://www.ukcdogs.com/spinone-italiano (Spinone weight)."
  ],
  "related": [],
  "changelog": [
    {
      "date": "2026-09-28",
      "note": "The age from a birthday shows days too, so a 21-day-old puppy reads 21 days, not 0 days; mixed-breed labels read “Mixed breed (medium, 21 to 50 lb)”."
    }
  ]
}