Cat BMI Calculator — Feline Body Condition Score
Unlike dogs or humans, cats are assessed by Body Condition Score (BCS), not BMI. Enter your cat's current weight and the ideal weight set by your vet to find out how far from target your cat is — and which BCS band it falls into.
Weight unit
kg
kg
Overweight (BCS 7)
- 1
Weight ratio
5.2 ÷ 4.5 = 1.1556 - 2
Body weight vs ideal
1.1556 × 100 = 115.6
How does this calculator work?
Divide your cat's current weight by its vet-recommended ideal weight and multiply by 100. Values 85–115 % indicate healthy weight (BCS 4–6); 115–135 % indicates overweight (BCS 7); above 135 % indicates obese (BCS 8–9). This is a percentage-of-ideal approach, not the human BMI formula.
Formula
How this is calculated
Cats are not assessed with the human Body Mass Index (BMI = weight ÷ height²) because veterinary practice uses a different standard: the 9-point Body Condition Score (BCS), originally developed by Purina and widely adopted by veterinary associations. BCS 1–3 is underweight, 4–6 is ideal, 7 is overweight, and 8–9 is obese. A trained vet assigns BCS by feeling the ribs, waist, and abdominal fat — a purely visual/tactile scale.
This calculator gives a numeric proxy: the ratio of your cat's current weight to the ideal weight your vet has recommended (or the breed average). A ratio near 100 % corresponds to BCS 5 (ideal); ratios above 115 % correspond to BCS 6–7 (overweight); above 135 % to BCS 8–9 (obese). The BCS thresholds used here follow guidelines from the World Small Animal Veterinary Association (WSAVA, 2011).
Ideal weight varies considerably by breed — from about 3 kg for a Siamese to 7 kg or more for a Maine Coon. Your vet's individual assessment is always more reliable than any calculator. If you do not have an ideal weight from a vet, typical domestic shorthair targets are 3.5–5 kg for females and 4–6 kg for males.
Frequently asked questions
No. Human BMI uses height squared as a denominator because human body proportions are consistent. Cats have highly variable body shapes across breeds, and height is not a standard veterinary measurement. The Body Condition Score (BCS) system is the accepted clinical standard for cats.
The most reliable source is your vet's recommendation for your specific cat. As a starting point, the average domestic shorthair female targets 3.5–5 kg and male 4–6 kg, but these vary substantially with breed, build, and whether the cat is neutered.
Obese cats have a significantly elevated risk of diabetes mellitus, hepatic lipidosis (fatty liver disease), osteoarthritis, urinary tract disease, and reduced lifespan. Even a 10–15 % excess above ideal weight increases these risks noticeably.
TG we-Calculate Editorial Team. (2026). Cat BMI Calculator — Feline Body Condition Score [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/cat-bmi-calculator
TG we-Calculate Editorial Team. "Cat BMI Calculator — Feline Body Condition Score." TG we-Calculate. 2026. https://we-calculate.com/calculator/cat-bmi-calculator.
TG we-Calculate Editorial Team, "Cat BMI Calculator — Feline Body Condition Score," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/cat-bmi-calculator
@misc{wecalculate_cat_bmi_calculator, title = {Cat BMI Calculator — Feline Body Condition Score}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/cat-bmi-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?