Cat BMI Calculator & Body Condition Score
Calculate your cat's Body Mass Index (BMI) and Body Condition Score (BCS) to assess whether your cat is at a healthy weight. This calculator uses veterinary-validated methods including the 9-point Body Condition Scale and Feline BMI formula to determine if your cat is underweight, ideal weight, overweight, or obese.
Calculate Your Cat's BMI & Body Condition
Current Weight
Average cat: 8-10 lbs
Average cat: 3.5-4.5 kg
Body Condition Score (BCS) - 9 Point Scale
Assess your cat by looking and feeling. Can you see their ribs? Do they have a visible waist from above?
💡 Tip: Run your hands along your cat's sides. You should be able to feel ribs with slight pressure, similar to feeling the back of your hand.
Feline BMI (fBMI) - Optional
Measure leg length from top of patella (kneecap) to end of calcaneus (heel bone) for more precise BMI calculation
Typical: 12-16 cm
Typical: 4.7-6.3 inches
How Cat BMI & Body Condition Are Calculated
Calculation Methods
1. Body Condition Score (BCS) - Most Common Method:
Visual & Palpation Assessment
The 9-point BCS system evaluates body shape, rib palpability, waist definition, and abdominal fat. BCS 4-5/9 is ideal (15-20% body fat). Each point above or below ideal represents approximately 10% deviation from optimal weight.
2. Ideal Weight Calculation from BCS:
\( \text{Ideal Weight} = \frac{\text{Current Weight}}{\text{Weight Multiplier}} \)
Weight multipliers by BCS:
BCS 1: 0.80, BCS 2: 0.90, BCS 3: 0.95, BCS 4: 0.98
BCS 5: 1.00 (ideal), BCS 6: 1.10, BCS 7: 1.20
BCS 8: 1.30, BCS 9: 1.40
3. Feline Body Mass Index (fBMI):
\( \text{fBMI} = \frac{\text{Body Weight (kg)}}{\text{Leg Length (cm)}} \times 100 \)
Leg length measured from top of patella to end of calcaneus (heel). Normal fBMI ranges: Thin <24.6, Ideal 24.6-33.1, Overweight 33.1-40.3, Obese >40.3.
4. Weight to Lose/Gain Calculation:
\( \text{Weight Change Needed} = \text{Current Weight} - \text{Ideal Weight} \)
Positive value indicates weight loss needed; negative indicates weight gain needed. Safe weight loss rate: 1-2% of body weight per week.
Body Condition Score Visual Guide
Cat Weight Management Guide
✓ Healthy Weight Cats
- Maintain current feeding routine
- Provide daily play/exercise
- Monitor weight monthly
- Regular vet checkups
⚠️ Weight Loss Needed
- Consult vet before diet changes
- Reduce calories by 10-20%
- Increase activity gradually
- Target 1-2% weight loss/week
- Use measured portions
⚠️ Weight Gain Needed
- Veterinary examination essential
- Rule out underlying illness
- High-calorie quality food
- Frequent small meals
- Monitor closely
Frequently Asked Questions
What is a healthy BMI for cats?
Cats don't use traditional BMI. Instead, veterinarians use Body Condition Score (BCS) on a 9-point scale, where 4-5/9 is ideal. For Feline BMI (fBMI), normal range is 24.6-33.1. A BCS of 5/9 corresponds to approximately 15-20% body fat, which is considered optimal for cats. Each BCS point represents roughly 10% deviation from ideal weight.
How do I know if my cat is overweight?
Look at your cat from above - you should see a visible waist behind the ribs. Feel their sides - you should be able to feel ribs with slight pressure, but they shouldn't be prominently visible. From the side, the belly should have a slight upward slope (tummy tuck). If ribs are difficult to feel, there's no waist, and the belly sags or hangs, your cat is overweight (BCS 6-7/9) or obese (BCS 8-9/9).
What is the ideal weight for a cat?
Ideal weight varies significantly by breed and individual cat. Average domestic cats typically weigh 8-10 lbs (3.5-4.5 kg). Small breeds like Siamese may be healthy at 5-8 lbs, while large breeds like Maine Coons can weigh 15-25 lbs. The ideal weight is determined by body condition, not just pounds. A cat at BCS 5/9 is at their ideal weight regardless of the number on the scale.
How fast should my cat lose weight?
Safe weight loss for cats is 1-2% of body weight per week, or approximately 0.5-1 lb per month for an average cat. Rapid weight loss can cause hepatic lipidosis (fatty liver disease), a life-threatening condition. For a 12 lb cat, aim to lose 2-4 ounces per week. Weight loss should always be supervised by a veterinarian with regular weigh-ins every 2-4 weeks to monitor progress and adjust the plan as needed.
Why is cat obesity dangerous?
Obesity significantly increases risk of diabetes, arthritis, heart disease, high blood pressure, urinary problems, and shortened lifespan. Overweight cats are 2.8 times more likely to develop diabetes and have difficulty grooming, leading to skin problems. Obesity also complicates anesthesia and surgery. Studies show obese cats live an average of 2 years less than cats at healthy weight. Even modest weight loss can reduce these health risks substantially.
How often should I check my cat's weight?
For cats at ideal weight, check body condition monthly and weigh quarterly. For cats on weight loss programs, weigh every 2 weeks to monitor progress. For senior cats (over 7 years) or those with chronic conditions, monthly weight checks help detect problems early. Sudden weight loss (more than 2% in one week) or gain warrants immediate veterinary attention. Keep a weight log to track trends over time.