Measure your cat's rib cage circumference and lower back leg length for calculation.
If you can't feel your cat's ribs, she likely needs to lose weight.
The Feline Body Mass Index follows the same concept as the human BMI measurement where you look at a person's weight and height and work out the percentage of body mass made up of fat.
Measurements You Need to Calculate Your Cat's FBMI
While your cat is in a standing position, with the legs perpendicular to the ground and the head upright (good luck with that!):
Measure the circumference of your cat’s rib cage. (The level of the 9th rib is ideal.)
Now measure the length of the lower back leg from the knee to the ankle and write down both numbers, because with what is coming, you probably won’t remember them.
Calculating the FBMI
Divide the rib cage measurement by 0.7062 and subtract the length of the leg.
Divide that answer by 0.9156.
Subtract the leg length from that number, and that is your cat’s BMI.
Prefer not to use this formula? Follow the following rule of thumb:
If you can't feel your cat's ribs when you run your hand down her chest, she likely needs to lose a pound or two.
Some other tips for managing your cat's weight:
Feed high-quality food
Limit free feedings
Exercise freely
It's hard keeping an indoor cat trim but definitely worth the effort.
FAQs: Measuring Your Cat's FBMI
To calculate your cat's Feline Body Mass Index (FBMI), you need two measurements: rib cage circumference at the 9th rib level and lower back leg length from knee to ankle. Divide the rib cage measurement by 0.7062, subtract the leg length, then divide that result by 0.9156, and subtract the leg length again. This gives you your cat's BMI. The calculation can be tricky, so having your cat stand with legs perpendicular and head upright is essential for accurate measurements.
A simple rule of thumb to check if your cat is overweight is the rib test. Run your hand down your cat's chest - if you can't feel her ribs, she likely needs to lose a pound or two. This hands-on method is much easier than calculating the complex FBMI formula and gives you a quick assessment of your cat's body condition. If you're concerned about your cat's weight, consult your veterinarian for a professional evaluation and weight management plan.
For calculating your cat's BMI, you need two specific measurements taken while your cat is standing with legs perpendicular to the ground and head upright. First, measure the circumference of your cat's rib cage at the level of the 9th rib. Second, measure the length of the lower back leg from the knee to the ankle. Write down both numbers immediately since the calculation process can be complex and you'll likely forget the measurements otherwise.
To help your overweight cat lose weight, focus on three key areas: feed high-quality food, limit free feedings, and encourage exercise. Instead of leaving food out all day, establish scheduled meal times to control portions. Choose nutritionally dense, high-quality cat food that will satisfy your cat with smaller portions. Encourage activity through play and interactive toys. While keeping an indoor cat trim can be challenging, the health benefits make the effort worthwhile. Consult your veterinarian for a personalized weight management plan.
The Feline Body Mass Index (FBMI) follows the same concept as human BMI measurement, evaluating the percentage of body mass made up of fat by looking at specific body measurements rather than just weight. Unlike human BMI which uses height and weight, cat BMI uses rib cage circumference and leg length measurements. This system provides a more accurate assessment of your cat's body condition than weight alone, since cats can vary significantly in size and build while still being healthy.
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