Last updated: April 13, 2026

Cat BMI Calculator

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Table of contents

Feline Body Mass Index (FBMI)

Unlike human BMI, the cat BMI is calculated using body measurements. The Feline BMI was developed to estimate body fat percentage using the circumference of the ribcage and the length of the lower leg (knee to ankle).

How to measure

  • Ribcage circumference: Wrap a tape measure around the cat's chest, just behind the front legs, at the level of the 9th rib.
  • Leg length: Measure from the knee to the ankle on a hind leg.
Around the chest behind the front legs.
From knee to ankle on a hind leg.

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