Cat BMI & Body Condition Calculator

Feline Morphometric Adiposity, The Feline Body Mass Index (FBMI), and the 9-Point BCS

Evaluating feline obesity requires moving beyond standalone scale weight to objective Morphometric Adiposity Indexing. A large-framed Maine Coon may be lean and healthy at 16 lbs, whereas a petite Siamese is severely obese at 12 lbs.

Veterinary clinicians utilize two validated systems: the Feline Body Mass Index (FBMI)—developed by veterinary researchers using rib cage circumference and lower leg measurements—and the WSAVA 9-Point Body Condition Score (BCS) endorsed by the World Small Animal Veterinary Association (WSAVA).

The Feline Body Mass Index (FBMI) Equation:
FBMI = [ (Rib Cage Circumference in cm ÷ 0.706) - Lim Index Length in cm ] ÷ 0.9156
- FBMI < 15%: Underweight (Emaciated)
- FBMI 15% to 29%: IDEAL BODY FAT PERCENTAGE
- FBMI 30% to 42%: Overweight
- FBMI > 42%: Severely Obese

WSAVA 9-Point Body Condition Score Scale:
- BCS 1–3: Underweight (Ribs and spine easily visible with zero fat covering)
- BCS 4–5: IDEAL (Ribs easily palpable under light fat, visible waistline, minimal abdominal fat pad)
- BCS 6–7: Overweight (Ribs difficult to palpate, moderate fat padding over spine and belly)
- BCS 8–9: Obese (Massive fat deposits over lumbar spine, face, and distended abdomen)

The 3 Core Diagnostic Palpation Checks

1. The Rib Sweep Palpation: Gently run flat fingers along the cat's ribcage. You should feel individual ribs easily—similar to running fingers over the knuckles on the back of your flat hand.
2. The Aerial Hourglass Silhouette: Look down at your cat from directly above. An ideal cat exhibits a clear inward taper behind the ribs.
3. The Primordial Pouch Distinction: The primordial pouch is a loose, natural flap of skin on the lower belly that protects organs and aids flexibility. An obese cat possesses a hard, fat-filled, distended belly that sways heavily when walking.

Calculate target feeding portions with Cat Calorie Calculator, plan gradual reduction via Cat Weight Loss Planner, monitor senior adjustments using Cat Age Adjusted Feeding, and explore obesity prevention at WSAVA.