Cat BMI Calculator (Body Condition Estimate)
Cats don’t use the same BMI system as humans. This tool gives a simple body condition estimate using weight and measurements, plus an easy interpretation.
Quick answer
What this “Cat BMI” means
This is a practical body condition estimate using a simple feline body index: weight ÷ length² (with units handled automatically). It helps you spot trends, but it is not a medical diagnosis. For the gold standard, ask your vet for a Body Condition Score (BCS).
Best use: track changes over time for the same cat using the same measuring method.
Inputs
Enter your cat’s current weight.
Measure along the body (do not include the tail).
Optional: rib check (for a better interpretation)
This mirrors common BCS guidance.
Helps categorize the result.
Important note
A “cat BMI” is not a veterinary standard. The most widely used clinical method is a Body Condition Score (BCS) based on ribs, waist, and fat coverage. This calculator is a quick estimate to help you notice trends — it can’t replace a vet exam.
How this calculator works (formulas)
This tool uses a simple body index built from weight and body length. We normalize units so the index is comparable:
Step 1: Convert units
- kg = lb × 0.453592 (if weight entered in pounds)
- m = cm ÷ 100 or in × 0.0254 (if length entered in inches)
Step 2: Body index
Index = weight(kg) ÷ [length(m)]²
Step 3: Category & ideal range
We map the index to broad categories (underweight / ideal / overweight / obese). Then we compute an “ideal weight range” using the ideal index band:
Ideal weight = idealIndex × length²
The rib and waist checks nudge the category slightly to better match typical BCS observations.
FAQ
Do cats have a real BMI like humans?
Not in the same standardized way. Vets commonly use a Body Condition Score (BCS) based on physical assessment. This calculator is a simple measurement-based estimate to help track trends.
What is a healthy cat weight?
It depends on breed, frame size, and muscle mass. The best approach is a vet-assigned BCS and a target weight plan. This tool provides an estimate based on your cat’s length and a broad “ideal index” band.
How often should I re-check?
Monthly is a common cadence. Use the same scale and measure length consistently. If weight changes quickly or your cat seems unwell, talk to a vet.