How Much Should a Cat Weigh? Our Vet Explains

How much should a cat weigh?

The average healthy adult cat should weigh between 3.8 kg (7.9 lbs) – 6 kg (13.2 lbs), however, the number on the scales is just a guideline. A body condition score is a more accurate assessment of a cat’s ideal weight as this takes into account the cat’s overall build and size.

This score ranges from 1 – 9. The World Small Animal Veterinary Association outlines the body condition score as follows:

  • 1 – Ribs are visible on shorthaired cats and there is no palpable fat. Lumbar vertebrae and ilia are easily palpated. Severe abdominal tuck.
  • 2 – Ribs are easily visible on shorthaired cats and there is no palpable fat. Lumbar vertebrae are obvious. There is a pronounced abdominal tuck.
  • 3 – Ribs are easily palpable and there is minimal palpable fat. Lumbar vertebrae are obvious. There is an obvious waist behind the ribs. Minimal abdominal fat.
  • 4 – Ribs are palpable with minimal fat covering. There is a noticeable waist behind the ribs and a slight abdominal tuck. The abdominal fat pad is absent.
  • 5 ideal weight – The cat is well proportioned, ribs have a slight fat covering and palpable and abdominal fat is minimal.
  • 6 – The ribs are palpable with a slight excess in the fat covering. The waist and abdominal fat pad are distinguishable but not obvious. There is no abdominal tuck.
  • 7 – The ribs are not obviously palpated, and there is a moderate-fat covering. The waist is poorly discernable and there is an obvious rounding of the abdomen. There are fat deposits over the lumbar area.
  • 8 – Ribs are not palpable under a heavy layer of fat. The waist is absent. There is an obvious rounding of the abdomen and a prominent fat pad. There are fat deposits over the lumbar area.
  • 9 obese – Ribs are not palpable under a heavy layer of fat. There are fat deposits over the lumbar area, face and limbs. The abdomen is distended and there is no waist. There are extensive abdominal fat deposits.

Cats don’t vary in size as much as dogs do; however, there can be quite a difference between breeds of cat or even body type as well as gender. Some are small and muscular, long and lean or large and solid. Some of the larger breeds such as Maine Coons and Siberians can tip the scales beyond 6 kg and be well within a healthy weight.

Healthy weight for cats

The following table is a guideline only, evaluating a cat’s body condition is a more accurate way to determine if a cat is overweight or underweight. Male cats tend to weigh 2 to 4 lbs more than female cats of the same breed or body type. It is important to note that being spayed or neutered is not an excuse for an overweight cat.

Small to medium cats or breeds 3.5 to 5.5 kg (7.7 to 12.1 pounds)
Large cats or breeds 6-8 kg (13 to 17.6 pounds)

Do senior cats lose weight over time? Many senior cats will lose weight as they age. This is almost always secondary to one of the “classic” senior cat health problems such as kidney failure or hyperthyroidism. If your cat drops her body conditions score and hits a “3” you need to have her evaluated. A thorough veterinary exam, coupled with a complete blood workup should help you to find the cause. While many senior cat health problems can’t be cured, most of them can be controlled, giving your cat good quality of life.

Evaluating body condition

The number on the scales can give you a general picture of your cat’s weight, however, as we know, cats come in all shapes and sizes and therefore instead of focusing entirely on a number on the scales, a better way to determine if your cat is overweight or underweight is to go by look and feel.

  • Ribs: You should be able to feel the ribs when you run your hands along your cat’s sides, but they should have a thin covering of fat over them. Ribs that can easily be seen or felt are an indicator your cat is underweight. If you can’t feel the ribs at all, he is overweight.
  • Spine: The same goes for the spine, you should be able to feel it when you run your fingers along the back, but it shouldn’t be overly noticeable. If you stand over your cat, you should see the torso tuck in where the ribs finish. An exaggerated tuck is a sign of an underweight cat; overweight cats may have no tuck at all.
  • Keep a record: Veterinarians usually routinely weigh cats during visits, it is a good idea to make a note of your cat’s weight when he is fit and well so that you can use this number to determine any weight gain or weight loss in the future. Make a file for your cat where all of his veterinary papers are stored and keep a note of his healthy weight in there.

Either way, you should see a veterinarian to determine if there is a medical reason your cat is underweight or overweight.

Causes of weight loss in cats

  • Inadequate amount of food – Underfeeding, inter-cat bullying or a deficient diet.
  • Hyperthyroidism – This endocrine disease is usually due to a benign tumour of the thyroid gland.
  • Diabetes mellitus – As glucose is unable to enter the cells, the body will become starved of energy, so it begins to break down fat stores as an alternative fuel source.
  • Kidney disorders such as acute or chronic kidney disease and glomerulonephritis
  • Addison’s disease – An endocrine disorder of the adrenal glands which results in a deficiency in the production of corticosteroids.
  • Cancer – Many types of cancer can lead to weight loss and wasting in cats.
  • Dental problems, which can make eating painful.
  • Pregnancy and lactation – Female cats need considerably more calories when they are pregnant or nursing a litter of kittens.
  • Intestinal parasites such as roundworm, cryptosporidiosis, and giardiasis – Weight loss can occur if the parasite is competing with the cat for nutrients (in the case of roundworms), or by causing vomiting and diarrhea in cats.
  • Exocrine pancreatic insufficiency – A disease caused by a failure of the pancreas to secrete adequate levels of pancreatic enzymes which result in an inability to digest food.
  • Feline immunodeficiency virus – Viral infection, similar to HIV in humans.
  • Feline leukemia virus – FeLV is a viral infection caused by reovirus, which is in the same family as the feline immunodeficiency virus. It is an oncovirus, meaning it can cause cancer. It also suppresses the immune system.
  • Heartworm disease
  • Inflammatory bowel disease
  • Liver disease
  • Pancreatitis – An inflammation of the pancreas due to pancreatic enzymes which begin to break down and digest the organ.
  • Pyometra – Infection of the uterus.
  • Stress – Can lead to a loss of appetite.

What should I do if my cat is underweight?

If your cat is thin and doesn’t respond weightwise to increased food, you need to look at the list above. Your veterinarian may recommend blood work, radiographs (x-rays) or other diagnostic testing to rule out the causes listed above. Specific treatment will depend on what cause may be found. Young cats, especially young males, may simply burn off calories faster than they can consume them. As long as they are healthy otherwise, you just observe and wait for some maturity.

Cats who are not maintaining weight may benefit from appetite stimulants such as Mirataz (mirtazapine) or Elura (capromorelin). At home, you can try things like adding the juice from a can of tuna to entice your cat to eat more.

Very ill cats may benefit from having a feeding tube placed. Under anesthesia, your veterinarian puts a soft tube through your cat’s body wall and into her stomach. This is left in place and you can administer a food slurry periodically over the day.

Causes of weight gain in cats

  • Overfeeding
  • Acromegaly – A syndrome related to a tumor of the pituitary gland in the brain. Excessive amounts of growth hormone are produced by these tumors. Many cats will develop insulin-resistant diabetes as a result.
  • Hypothyroidism – A deficiency of thyroid hormone and is quite uncommon in cats. The low levels means a lower metabolic rate, so a cat will burn less calories off than expected.
  • Pregnancy

How to help a healthy cat lose excessive weight?

If your cat gains weight between vet visits (and wasn’t skinny to begin with), you need to work at dropping those extra ounces or pounds. Added weight predisposes your cat to various inflammatory disorders and to orthopedic problems such as arthritis. Diabetes Mellitus in cats is also associated with being obese.

Losing weight should be a two-pronged attack. Your cat needs fewer calories going in and some extra activity to help burn the extra calories she already has. This should also be done with your veterinarian’s guidance. Rapid weight loss can lead to hepatic lipidosis – a liver disorder that can be fatal.

Options for weight loss diets can include cutting back on your cat’s normal diet or trying a diet specifically designed for feline weight loss and weight management. If you elect to try a weight loss diet, remember to switch over gradually. The usual recommendation is 75% current diet with 25% new diet for 3 to 5 days, the 50/50 for 3 to 5 days, then 75% new and 25% current for 3 to 5 days before a total phase-out of the current diet.

Weight loss is easiest if you feed meals so you can monitor exactly how much your cat is eating, If you have multiple cats you will need to feed them separately for a time.

Meanwhile, up the ante on activity. Set aside a set amount of time to play with your cat daily. A feather wand is fun and gets your cat up and moving. Some cats will retrieve. Ambitious owners can make a mini agility course for their cats (there are actually feline agility competitions!). Many cats can learn to walk on a leash and may enjoy walks. This generally works best if your cat leads and you follow 😊

How much should a cat eat?

The best way to calculate a cat’s daily requirements is to calculate your cat’s resting energy requirements (RER) which is the amount of energy (in calories) expended in a day without any activity; it is similar to basal metabolic requirements. The different RERs shown here are for different life stages and dietary requirements:

  • Growing kittens – RER x 2.5
  • Maintenance for a desexed adult cat – RER x 1.2
  • Maintenance for an entire adult cat – RER x 1.4
  • Obese prone – RER x 1
  • Weight loss – RER x 0.8

RER is resting energy requirement – the number of calories your cat needs for basic life maintenance. That means how much energy she needs to take in daily to cover necessary body functions such as breathing, her heart beating, digesting food, keeping her brain active and any needed locomotion.

This RER can be calculated by multiplying the animal’s body weight in kilograms raised to the ¾ power by 70. If the complicated math overwhelms you, use this cat calorie calculator from The Pet Nutrition Alliance or read our chart: How many calories should a cat eat per day?