{
  "id": "cat-age",
  "version": "f1284abeb8cf",
  "status": "published",
  "name": "Cat Age Calculator",
  "question": "What is my cat’s age in human years?",
  "summary": "Converts a cat’s age, from its birthday or in years and months, to human-equivalent years on the AAHA/AAFP feline age chart, and names its life stage.",
  "category": "days",
  "subcategory": "age",
  "url": "https://www.acalculator.org/days/cat-age-calculator",
  "markdown": "https://www.acalculator.org/days/cat-age-calculator.md",
  "kind": "function",
  "method": "human years on straight lines through (0 months, 0), (3, 4), (6, 10), (12, 15), (18, 21), (24, 24); from 24 months, human years = 24 + 4 × (cat years − 2).",
  "assumptions": [
    "The chart is the AAHA/AAFP and International Cat Care feline age chart: 3 months = 4, 6 months = 10, 12 months = 15, 18 months = 21, 2 years = 24, then 4 human years for each cat year.",
    "Between the chart’s points, the human age is read on a straight line, by whole months.",
    "A birthday counts completed months up to the age-on date; days past the last whole month are not counted.",
    "Life stages follow the 2021 AAHA/AAFP guidelines by completed years: kitten under 1, young adult 1 to 6, mature adult 7 to 10, senior over 10.",
    "The chart is an average for all cats; it does not depend on breed or size."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "known": {
        "title": "What do you know?",
        "description": "Whether you know the cat’s birthday or its age in years and months.",
        "type": "string",
        "enum": [
          "birth",
          "age"
        ]
      },
      "birth": {
        "title": "Cat’s birthday",
        "description": "The day the cat was born, or your best guess.",
        "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": "The cat’s age in whole years.",
        "type": "integer",
        "minimum": 0,
        "maximum": 40
      },
      "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 AAHA/AAFP chart, read on a straight line between its points.",
      "format": "number"
    },
    "stage": {
      "label": "Life stage",
      "description": "The AAHA/AAFP 2021 life stage: kitten, young adult, mature adult, or senior.",
      "format": "text"
    },
    "age": {
      "label": "Cat’s age",
      "description": "The cat’s age in whole years and months.",
      "format": "duration"
    },
    "totalMonths": {
      "label": "Age in months",
      "description": "The cat’s age in whole months.",
      "format": "integer"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "known": "birth",
      "birth": "2021-10-02",
      "on": "2026-10-02",
      "years": 5,
      "months": 0
    },
    "outputs": {
      "human": 36,
      "stage": "Young adult",
      "age": {
        "years": 5,
        "months": 0
      },
      "totalMonths": 60
    },
    "text": "A cat of 5 years is about 36 in human years (Young adult)."
  },
  "examples": [
    {
      "given": {
        "known": "age",
        "years": 2,
        "months": 0
      },
      "expect": {
        "human": 24,
        "stage": "Young adult",
        "totalMonths": 24
      },
      "source": "AAHA/AAFP and International Cat Care feline age chart, as printed by IAMS (https://www.iams.com/cat/cat-articles/calculating-your-pets-age-cat-years, retrieved 2026-10-01): 2 years = 24 human years; 2021 AAHA/AAFP Feline Life Stage Guidelines (https://catvets.com/resource/aaha-aafp-feline-life-stage-guidelines/): young adult 1 to 6 years"
    },
    {
      "given": {
        "known": "age",
        "years": 10,
        "months": 0
      },
      "expect": {
        "human": 56,
        "stage": "Mature adult"
      },
      "source": "AAHA/AAFP and International Cat Care feline age chart, as printed by IAMS (https://www.iams.com/cat/cat-articles/calculating-your-pets-age-cat-years): 7 to 10 years = 44 to 56; hand calculation in content.mdx: 24 + 4 × 8 = 56"
    },
    {
      "given": {
        "known": "age",
        "years": 0,
        "months": 9
      },
      "expect": {
        "human": 12.5,
        "stage": "Kitten"
      },
      "source": "AAHA/AAFP and International Cat Care feline age chart, as printed by IAMS (https://www.iams.com/cat/cat-articles/calculating-your-pets-age-cat-years): 6 months = 10, 12 months = 15; hand calculation in content.mdx: 10 + 5 × 3 ÷ 6 = 12.5"
    },
    {
      "given": {
        "known": "birth",
        "birth": "2011-03-15",
        "on": "2026-09-30"
      },
      "expect": {
        "human": 78,
        "stage": "Senior",
        "age": {
          "years": 15,
          "months": 6
        },
        "totalMonths": 186
      },
      "source": "AAHA/AAFP and International Cat Care feline age chart, as printed by IAMS (https://www.iams.com/cat/cat-articles/calculating-your-pets-age-cat-years): 15 years = 76; hand calculation in content.mdx: 24 + (186 − 24) ÷ 3 = 78; Python: 186 months"
    }
  ],
  "sources": [
    "American Animal Hospital Association and American Association of Feline Practitioners, 2021 AAHA/AAFP Feline Life Stage Guidelines, life stage definitions, retrieved 2026-10-01. https://catvets.com/resource/aaha-aafp-feline-life-stage-guidelines/",
    "Quimby J, et al. 2021 AAHA/AAFP Feline Life Stage Guidelines. Journal of Feline Medicine and Surgery, 2021, 23(3): 211–233, Table 1 (life stages), retrieved 2026-10-01. https://pmc.ncbi.nlm.nih.gov/articles/PMC10812130/",
    "IAMS, Cat age chart (from the guidelines of AAHA, AAFP and International Cat Care), retrieved 2026-10-01. https://www.iams.com/cat/cat-articles/calculating-your-pets-age-cat-years"
  ],
  "related": [
    "dog-age",
    "birthday"
  ],
  "changelog": []
}