Pet BMI
Free Pet BMI calculator with clear step-by-step results.
About Pet BMI
Pets have no useful height-based body mass index, so condition is assessed as the percentage above ideal weight, cross-checked against the nine-point body condition score where each point above five represents roughly 10% excess. Safe loss rates are 1% of ideal body weight per week for dogs and 0.5% for cats.
Formulas
Excess weight
Excess % = (current weight - ideal weight) / ideal weight x 100
Safe loss rate
Weekly target = ideal weight x 1% for dogs, 0.5% for cats
Worked example
With the default values below, Pet BMI returns Weight above ideal of 18.5%. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Speciesone of Dog, Cat
- Dog
- Current weightaccepts 0.3–100 kg
- 32 kg
- Ideal weightaccepts 0.3–100 kg
- 27 kg
- Body condition score (1-9)accepts 1–9
- 7
Results
- Weight above ideal
- 18.5% %
- Weight category
- Overweight
- Excess weight to lose
- 5.00 kg
- Weeks at a safe loss rate
- 19 weeks
Step by step
- 1Values used
- 2Excess weight
- 3Safe loss rate
- 4Weight above ideal= 18.5 %
- 5Weight category= Overweight
- 6Excess weight to lose= 5.00 kg
- 7Weeks at a safe loss rate= 19 weeks
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
- Not a veterinary diagnosis. Weight loss plans for pets should be designed and monitored by a veterinarian, particularly where there is underlying disease or medication involved.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Not a veterinary diagnosis. Weight loss plans for pets should be designed and monitored by a veterinarian, particularly where there is underlying disease or medication involved.
Frequently Asked Questions
How do I find the ideal weight?
Your vet can estimate it from breed, frame and a hands-on body condition assessment. Breed averages alone are unreliable because frame size varies widely within a breed.
Why must cats lose weight more slowly?
Rapid calorie restriction in cats can trigger hepatic lipidosis, a serious liver condition. Feline weight loss must be gradual and supervised.