How much should my cat weigh?

Most domestic cats are healthy at somewhere around 8 to 11 lb (3.5 to 5 kg), but frame size varies a lot. A big Maine Coon can be lean at 16 lb while a petite cat is overweight at 11. That’s why vets judge by body shape, using a body condition score, rather than by a single number. This cat weight calculator does the same: it estimates your cat’s ideal weight from its current weight and body condition score, or uses the target your vet gave you.

Score your cat’s body condition

Run your hands along your cat’s sides, look down from above, then look from the side:

Score	What you see and feel	Roughly above ideal
4–5 (ideal)	Ribs easy to feel under a thin layer of fat. A clear waist from above and only a small belly pouch.	0%
6	Ribs felt with a little pressure. Waist present but not obvious.	about 10%
7	Ribs hard to feel under fat. Waist barely visible, rounded belly.	about 20%
8	Ribs very hard to feel. No waist, fat over the lower back and a hanging belly.	about 30%
9	Heavy fat over the chest, spine and base of the tail. Belly clearly bulges.	40% or more

The percentages are rough estimates that line up with standard definitions. The British Veterinary Association, for example, treats a score of 8 or 9, or 30% above ideal weight, as obese. Your vet can score your cat properly in a few seconds at the next visit.

How the weight-loss plan is worked out

The calorie target is 0.8 times the resting energy requirement (RER) at your cat’s target weight, the weight-loss level listed by the Pet Nutrition Alliance:

Calories = 0.8 × 70 × (target weight in kg)^0.75

The timeline assumes a slow, steady loss of about 0.5 to 1% of body weight a week. That pace is deliberately gentle, for a good reason.

Never starve a cat or cut its food sharply. When cats eat too little, fat floods the liver and can cause hepatic lipidosis (fatty liver disease), which can be fatal. Overweight cats are most at risk. Plan weight loss with your vet, and call them straight away if your cat stops eating for more than a day.

An example: Tiger weighs 14 lb and scores 7 out of 9, so he’s about 20% over his ideal of roughly 11.7 lb. His weight-loss target is about 195 kcal a day. Losing 2.3 lb gently will take somewhere around 16 to 33 weeks, and that slow pace is the safe one.

Tips that actually help cats slim down

Measure everything. Weigh dry food on a kitchen scale. Free-feeding from a full bowl makes weight loss very hard.
Add wet food. It has fewer calories per bite and more water, so cats feel full on less. The cat food calculator handles wet and dry mixes.
Make food work for them. Puzzle feeders and spreading small portions around the house add activity.
Play every day. Two or three short sessions with a wand toy burn energy and reduce boredom eating.
Weigh every two weeks and adjust by about 10% if progress stalls.

Why it’s worth it

Overweight cats have higher risks of diabetes, arthritis, urinary problems and skin issues, partly because they can’t groom properly. Many cats with diabetes improve, and some even go into remission, after losing weight under vet care.

Common questions

What is a healthy weight for a cat?

For many cats it’s around 8 to 11 lb, but the right weight depends on frame and breed. A body condition score of 4 to 5 out of 9 is the target.

How fast can a cat safely lose weight?

Slowly. Around 0.5 to 1% of body weight a week is a common, cautious goal. For a 14 lb cat, that’s only about an ounce or two a week.

How many calories should an overweight cat eat?

A common starting point is 0.8 times the resting energy requirement at the target weight, which is what this calculator shows. Your vet may adjust it.

Is my cat fat or just fluffy?

Feel, don’t look. Long fur hides a lot. If you can feel the ribs easily under a thin layer, your cat is probably fine.

What about kittens?

Kittens shouldn’t diet. Use the kitten age calculator to check they’re growing normally instead.

Sources

Last reviewed November 5, 2026.