{
  "id": "dog-weight",
  "version": "246606f6553f",
  "status": "published",
  "name": "Dog Weight Calculator",
  "question": "Dog weight: is my dog overweight?",
  "summary": "Estimates a dog’s ideal weight from its current weight and body condition score (9-point scale), how much it is over, and how many weeks a safe weekly weight loss takes, with the weight drawn week by week.",
  "category": "biology",
  "subcategory": "animals",
  "url": "https://www.acalculator.org/biology/dog-weight-calculator",
  "markdown": "https://www.acalculator.org/biology/dog-weight-calculator.md",
  "kind": "function",
  "method": "ideal weight = current weight ÷ (1 + 0.1 × (BCS − 5)) = 10 × weight ÷ (BCS + 5) for a score of 5 to 9 (4 is ideal); weeks = the first whole n with weight × (1 − rate)ⁿ ≤ ideal weight.",
  "assumptions": [
    "Uses the 9-point body condition score: 4 and 5 are ideal, and each point above 5 is about 10% over ideal weight (6 is 10%, 7 is 20%, 8 is 30%, 9 is 40%), as in the AAHA 2014 weight management guidelines. It is an estimate: your vet can check the score and the target.",
    "Scores of 1 to 3 (underweight) give no answer here.",
    "Each week the dog loses the chosen percent of its weight at the start of that week; the AAHA guidelines give 1% to 2% a week for dogs. The weeks count to the first weekly weigh-in at or below the ideal weight.",
    "Weights are from 0.2 to 150 kg (0.44 to 331 lb). The chart shows kilograms."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "w": {
        "title": "Current weight",
        "description": "Your dog’s weight today.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "mass",
        "minimum": 0.2,
        "maximum": 150
      },
      "bcs": {
        "title": "Body condition score",
        "description": "Your dog’s body condition score on the 9-point scale, from 1 (very thin) to 9 (very obese); 4 and 5 are ideal.",
        "type": "string",
        "enum": [
          "1",
          "2",
          "3",
          "4",
          "5",
          "6",
          "7",
          "8",
          "9"
        ]
      },
      "rate": {
        "title": "Weight loss per week",
        "description": "The share of body weight to lose each week, from 0.5% to 2%; the AAHA guidelines give 1% to 2% for dogs.",
        "type": "number",
        "x-unit": "percent",
        "minimum": 0.5,
        "maximum": 2
      }
    }
  },
  "outputs": {
    "ideal": {
      "label": "Ideal weight (lb)",
      "description": "The estimated ideal weight in pounds: current weight ÷ (1 + 0.1 × (score − 5)), or the current weight at a score of 4 or 5.",
      "format": "number"
    },
    "idealKg": {
      "label": "Ideal weight (kg)",
      "description": "The estimated ideal weight in kilograms.",
      "format": "number"
    },
    "category": {
      "label": "Body condition",
      "description": "Ideal, above ideal, overweight or obese, from the score.",
      "format": "text"
    },
    "over": {
      "label": "Over ideal weight",
      "description": "How much heavier than ideal the dog is, as a percent of the ideal weight: 10% per score point above 5.",
      "format": "percent"
    },
    "lose": {
      "label": "Weight to lose",
      "description": "Current weight − ideal weight, in pounds.",
      "format": "number"
    },
    "loseKg": {
      "label": "Weight to lose (kg)",
      "description": "Current weight − ideal weight, in kilograms.",
      "format": "number"
    },
    "weeks": {
      "label": "Weeks to ideal weight",
      "description": "Whole weeks until the weekly weight, losing the chosen percent of body weight each week, is at or below the ideal weight.",
      "format": "integer"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "w": 27.2155422,
      "bcs": "7",
      "rate": 1
    },
    "outputs": {
      "ideal": 50,
      "idealKg": 22.6796185,
      "category": "Overweight",
      "over": 20,
      "lose": 10,
      "loseKg": 4.5359237,
      "weeks": 19
    },
    "text": "Ideal weight: about 50 lb (22.7 kg) for a 60 lb dog (Overweight)."
  },
  "examples": [
    {
      "given": {
        "w": 27.2155422,
        "bcs": "7",
        "rate": 1
      },
      "expect": {
        "ideal": 50,
        "idealKg": 22.6796185,
        "over": 20,
        "lose": 10,
        "loseKg": 4.5359237,
        "weeks": 19,
        "category": "Overweight"
      },
      "source": "Brooks et al. (2014), AAHA Weight Management Guidelines for Dogs and Cats, J Am Anim Hosp Assoc 50(1):1–11 (BCS 7/9 is about 20% over ideal; lose 1–2% of body weight a week), https://www.researchgate.net/publication/258444230_2014_AAHA_Weight_Management_Guidelines_for_Dogs_and_Cats; hand calculation in content.mdx: 60 ÷ 1.2 = 50 lb; ln(50/60) ÷ ln(0.99) = 18.14, so 19 weeks"
    },
    {
      "given": {
        "w": 30,
        "bcs": "9",
        "rate": 2
      },
      "expect": {
        "ideal": 47.24191332533091,
        "idealKg": 21.428571428571427,
        "over": 40,
        "lose": 18.896765330132364,
        "loseKg": 8.571428571428571,
        "weeks": 17,
        "category": "Obese"
      },
      "source": "Brooks et al. (2014), AAHA Weight Management Guidelines (BCS 9/9 is about 40% over ideal); hand calculation in content.mdx: 30 ÷ 1.4 = 21.43 kg; ln(1 ÷ 1.4) ÷ ln(0.98) = 16.65, so 17 weeks"
    },
    {
      "given": {
        "w": 9.979032140000001,
        "bcs": "6",
        "rate": 1.5
      },
      "expect": {
        "ideal": 20,
        "idealKg": 9.0718474,
        "over": 10,
        "lose": 2,
        "loseKg": 0.90718474,
        "weeks": 7,
        "category": "Above ideal"
      },
      "source": "hand calculation in content.mdx: 22 ÷ 1.1 = 20 lb; ln(1 ÷ 1.1) ÷ ln(0.985) = 6.31, so 7 weeks"
    },
    {
      "given": {
        "w": 25,
        "bcs": "5",
        "rate": 1
      },
      "expect": {
        "idealKg": 25,
        "over": 0,
        "lose": 0,
        "loseKg": 0,
        "weeks": 0,
        "category": "Ideal"
      },
      "source": "hand calculation in content.mdx: a score of 5 is ideal, so the ideal weight is the current weight"
    }
  ],
  "sources": [
    "Brooks, D., J. Churchill, K. Fein, D. Linder, K. E. Michel, K. Tudor, E. Ward, and A. Witzel (2014). 2014 AAHA Weight Management Guidelines for Dogs and Cats. Journal of the American Animal Hospital Association 50(1), 1–11 (9-point BCS: 6/9 about 10% over ideal, 7/9 about 20%; weight loss of 1–2% a week for dogs). https://www.researchgate.net/publication/258444230_2014_AAHA_Weight_Management_Guidelines_for_Dogs_and_Cats",
    "Laflamme, D. (1997). Development and validation of a body condition score system for dogs. Canine Practice.",
    "American Animal Hospital Association, Body Condition Scoring (BCS) Systems (descriptions of the 9-point scale). https://www.aaha.org/public_documents/professional/guidelines/weightmgmt_bodyconditionscoring.pdf"
  ],
  "related": [
    "puppy-weight",
    "dog-age"
  ],
  "changelog": [
    {
      "date": "2026-09-30",
      "note": "Metric heads the result with the ideal weight in kg and names kg first in the answer."
    }
  ]
}