Cat Weight Calculator

How’s the Weight, Doc?

This is a question many pet parents, both kitty and pup parents alike, ask during their visits with their vet, but it’s probably a discussion that could still be had more often.

According to the latest 2018 results from the Association for Pet Obesity Prevention (APOP), which surveys pet parents and veterinary clinics about every two years, about 70% of parents would like to have cat weight loss and diet discussions with their vet, though only about 60% reported having these chats during visits.

This implies that more pet parents want to have these discussions and they need to be prompted more. Some veterinarians are afraid of inadvertently offending a pet parent by telling them that their cat is overweight. But on the flip side, a pet parent may think their cat’s weight is not an issue if their vet doesn’t say anything about it.

A calculator tool can be helpful to bridge this gap, as it can create a great starting point for those discussions. Instead of assuming your kitty’s weight is probably fine, or asking a generic question like “How’s the weight, doc?” The question can instead be “The online calculator I used said Kitty was about 2lb overweight. What can we do about that?”

How do I calculate my cat’s ideal weight?

A majority of cats will fall between a range of 8-12 pounds for ideal weight. The Association for Pet Obesity Prevention (APOP) has a small chart of ideal weights for dogs and cats. As you can see there, with only a couple exceptions, many cats fall within that range. The main exception is for Maine Coon cats, who normally tend to be much larger in size than other cat breeds.

Also Read:How much should I feed my cat

But if you want to be very scientific about it, start with assessing your cat’s body condition score (BCS), which essentially evaluates fat percentage and helps determine a good weight regardless of skeletal size.

For a body condition score scale of 1-5, as we use for our calculator, here is how each level roughly equates to an ideal weight:

Then, to calculate an ideal weight, use this formula:
Ideal weight = current weight x (100% – % overweight).

Here’s an example for a 15lb cat, estimated at a BCS of 5 (30% overweight): 

Ideal weight = 15lb x (100% – 30%)

Ideal weight = 15 x 70% (multiply by 0.7)

Ideal weight = 10.5lb

What is too heavy for a cat?

This largely depends on body fat percentage, which is where the body condition score (BCS) becomes very important. An ideal body fat percentage for any cat is about 20%, which equates to a body condition score of 3 on a 1-5 scale.

A cat with this body condition has a light fat covering, has ribs and hips that can be felt but not easily seen, and has a clear waistline and tummy tuck back towards the groin.

Most cats should have an ideal weight somewhere between 8-12 lb. But this depends on skeletal size. Even among cats from the same litter, there can be a couple pounds of difference between them. Maine Coon cats are one breed that tends to exceed this normal range with some Maine Coons normally weighing up to 25lb.

You can look at how long your cat is for an idea of average skeletal size. Most cats are about 18 inches in length (not including their tail). If your cat exceeds this average length, a heavier weight may be more normal. Likewise, if your cat is shorter than 18 inches, it’s possible your kitty should weigh on the lower side below 10lb.

How much should I feed my cat to lose weight?

The best way is to first know your cat’s ideal weight so that you know how much your cat needs to lose. Our cat weight calculator can help you find out your cat’s ideal weight and how much food to feed based on the kilocalories (kcal) your kitty’s food contains.

A simple way to estimate where to start, regardless of how overweight your cat is, would be to assume, for an average cat with an ideal weight of 10 lb, that they should take in about 180-200 calories per day. To help with weight loss, we then want to aim to feed about 80% of that. If we consider 200 calories per day, 80% would be 160 calories.

To turn this into actual feeding amounts, take the kilocalorie amount in a can or cup of the food. Divide your cat’s energy need (160 kcal in our example) by the kcal amount on the package label. If it’s 350 kcals for example, then your cat needing 160 kcal per day would need just under ½ cup of food per day.

Do cats lose weight as they age?

Age by itself does not necessarily correlate with noticeable weight loss, though this is a common perception. A little bit of muscle loss can occur with advancing age, so you might notice an old kitty exceeding 15 years or so of age having a little thinning along the spine. This is mildly noticeable at best.

But significant weight loss is usually due to some underlying disease process, whether it be kidney disease, inflammatory bowel, diabetes, a form of cancer, etc.. As it happens, we tend to see more serious disease causing weight loss in cats that are older. So while noticeable weight loss may not be due to age itself, the disease conditions that come with advancing age contribute a lot to weight loss.

We can also actually see just the opposite in some cats. If activity level declines, as it’s wont to do with age, a cat’s energy needs will decrease, which can lead an inactive cat to gain weight instead. But every cat is different, so if you’re not sure if your cat has gained or lost weight and whether you should be concerned, make sure to bring these changes up at your cat’s next veterinary exam.

– Dr. Chris Vanderhoof, DVM