How this calculator works
Measure standing height at the withers, the highest point of the shoulders, and weigh the dog. The arithmetic uses kilograms and metres regardless of display units. Dogs of different builds can have the same index but different body fat. Breed average weights are not BMI diagnostic limits and are deliberately not used as such.
Formula
Index = weight in kg / (height in m)². Weight = index × height². Height = square root of (weight / index).
Worked example
A 20 kg dog measuring 50 cm has an index of 20 / 0.5² = 80 kg/m². A 9 kg dog at 30 cm gives 100 kg/m². Neither number on its own diagnoses obesity.
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Frequently asked questions
Does a human BMI chart apply?
No. Human diagnostic ranges must not be applied to dogs.
Why are there no breed-specific healthy limits?
A validated breed-specific diagnostic reference is needed before assigning such limits. This tool supplies only the arithmetic.
What should I use for a feeding decision?
Use body condition, muscle condition, weight history and a veterinary nutrition assessment.