Cat BMI Calculator

Scientific body fat estimation (FBMI) using skeletal measurements for all feline breeds.

Measurements (cm)

Rib Cage Circumference

Measure around the rib cage at the 9th rib level (just behind the front legs).

Lower Leg Length (LIM)

Measure from the middle of the kneecap (patella) to the heel bone.

Feline Body Mass Index

37.7

Calculated FBMI

Estimated body fat %

UnderIdealOverObese

Weight StatusOverweight

Weight reduction for cats should always be supervised by a vet to avoid nutrient deficiencies.

Why BMI for Cats?

Unlike humans, cats have vastly different bone structures. A 12lb Siamese is obese, while a 12lb Maine Coon is malnourished. The Feline Body Mass Index (FBMI) is a validated scientific method that uses skeletal ratios to determine actual body fat percentage, independent of breed size.

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Pro Tips

BCS check: You should be able to feel your cat's ribs easily with a light touch, like the back of your hand.
The Primordial Pouch: A saggy belly flap isn't necessarily fat—it's a protective skin layer inherited from wild ancestors.
Weight Loss Safety: Cats must lose weight slowly (1-2% body weight per week) to prevent Hepatic Lipidosis.
Hidden Risks: Obesity in cats is linked to osteoarthritis, breathing issues, and a 400% higher risk of diabetes.

Fun Facts

"Cats spend roughly 70% of their lives sleeping—no wonder they struggle with weight!"
"An 'ideal' cat has a visible waistline when viewed from above and a slight abdominal tuck from the side."
"A house cat's skeleton consists of ~244 bones (humans have 206)."
"Cats have a unique collarbone that allows them to squeeze through any space their head fits into."

Formula: FBMI = ((Rib / 0.7062) - Leg) / 0.9156

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