Cat Food Calculator
A cat’s daily calories are estimated as RER = 70 × (weight in kg)^0.75 times a life-stage factor (1.2–1.4 for a neutered adult). Split those calories between wet and dry food and divide by each food’s calories from the label.
Example: a 4 kg (8.8 lb) neutered adult cat has an RER of about 198 kcal and needs about 238–277 kcal a day.
How it works
RER (kcal/day) = 70 × (body weight in kg)^0.75 Daily calories = RER × life-stage factor Wet food = daily calories × wet share ÷ kcal per can Dry food = daily calories × dry share ÷ kcal per cup (or per gram)
Factors are from the 2021 AAHA Nutrition and Weight Management Guidelines (Box 1). We leave the wet food calories blank on purpose: cans and pouches vary too much, so use the number on your label. The 400 kcal/cup dry food default is an example only.
How to work out how much to feed your cat
- Weigh your cat. For weight loss, use the ideal weight your vet suggests.
- Choose the life stage. Neutered, intact, inactive, kitten, pregnant or nursing.
- Set the wet/dry split. Move the slider to the share of calories you want from wet food.
- Enter the label calories. kcal per can or pouch for wet food, and kcal per cup or per kg for dry food.
- Check and adjust. Weigh your cat regularly and adjust using the body condition score.
Life-stage factors (AAHA 2021)
| Life stage | Factor | kcal/day for a 4 kg (8.8 lb) cat |
|---|---|---|
| Neutered or spayed adult | 1.2–1.4 × RER | 238–277 |
| Intact adult | 1.4–1.6 × RER | 277–317 |
| Inactive adult | 1 × RER | 198 |
| Weight loss (enter ideal weight) | 0.8 × RER | 158 |
| Kitten (growing) | 2.5 × RER | 495 |
| Pregnant | 1.6–2 × RER | 317–396 |
| Nursing (lactation) | 2–6 × RER | 396–1,188 |
RER for 4 kg = 70 × 40.75 = 198 kcal/day. Kittens: 2.5 × RER while growing.
Frequently asked questions
How many calories does a cat need a day?
Multiply 70 by the cat’s weight in kg to the power 0.75, then by the life-stage factor. A 4 kg neutered adult cat needs about 238–277 kcal a day; a 5 kg neutered adult about 281–328 kcal.
How much wet food should I feed my cat?
Divide the calories you want from wet food by the kcal per can or pouch on the label. The calorie content of wet food varies a lot between brands and sizes, so check your label.
How much dry food should a cat eat?
Divide the dry-food calories by the kcal per cup on the bag. Weighing dry food in grams on a kitchen scale is more accurate than using a cup.
How fast should a cat lose weight?
Slowly. A review of feline obesity management recommends about 0.5–2% of body weight per week, and Cornell suggests 1–2%. Crash diets can cause hepatic lipidosis (fatty liver), so weight loss should be planned with your vet.
What about senior cats?
The AAHA table has no separate senior factor. Use the factor that fits your cat’s activity and neuter status, and ask your vet, especially if your senior cat is losing weight.
How many calories does a kitten need?
AAHA uses 2.5 × RER for growing kittens. Recalculate often, because kittens gain weight quickly.
When to see a vet
- Your cat has not eaten for more than a day. Cats that stop eating can develop fatty liver quickly.
- Weight loss you did not plan, or any weight change in a senior cat.
- You want to start a weight-loss plan.
- Your cat is pregnant, nursing, or has kidney disease, diabetes or another condition.
This is an estimate for general information, not veterinary advice. Every pet is different. Ask your veterinarian before changing your pet's diet, especially for puppies, kittens, pregnant or nursing pets, seniors, or pets with health conditions.
Sources
- AAHA. 2021 AAHA Nutrition and Weight Management Guidelines for Dogs and Cats, Box 1: Energy requirement calculations (RER/MER life-stage factors). www.aaha.org/wp-content/uploads/globalassets/02-guidelines/2021-nutrition-and-weight-management/resourcepdfs/nutritiongl_box1.pdf
- AAHA. 2021 AAHA Nutrition and Weight Management Guidelines for Dogs and Cats. www.aaha.org/resources/2021-aaha-nutrition-and-weight-management-guidelines/
- Merck Veterinary Manual. Nutritional Requirements of Small Animals; table: Daily maintenance energy requirements for dogs and cats. www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals
- Pet Nutrition Alliance. Calculating Calories Based on Pet Needs (RER/MER factors). petnutritionalliance.org/wp-content/uploads/2023/03/MER.RER_.PNA_.pdf
- WSAVA Global Nutrition Committee. Global Nutrition Guidelines and toolkit (body condition score charts). wsava.org/global-guidelines/global-nutrition-guidelines/
- WSAVA. Feeding treats to your cat (treats no more than 10% of daily calories). wsava.org/wp-content/uploads/2024/06/Feeding-treats-to-your-cat-v2.pdf
- Tufts Petfoodology. Should You Be Weighing Your Pet’s Food? (example cat food of 400 kcal per cup). sites.tufts.edu/petfoodology/2021/08/16/should-you-be-weighing-your-pets-food/
- Tufts Now. Wide Variation in Calorie Content among “Low Calorie” Pet Foods (2010). now.tufts.edu/2010/01/26/wide-variation-calorie-content-among-low-calorie-pet-foods
- Cornell Feline Health Center. Obesity. www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/obesity
- Cornell Feline Health Center. Hepatic lipidosis. www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/hepatic-lipidosis
- Hoelmkjaer KM, Bjørnvad CR. Management of obesity in cats. Vet Med (Auckl). Research and Reports (weight-loss rate 0.5–2% per week). doi.org/10.2147/VMRR.S40869
- Quimby J, Gowland S, Carney HC, et al. 2021 AAHA/AAFP Feline Life Stage Guidelines. J Feline Med Surg. 2021;23(3):211–233. doi.org/10.1177/1098612X21993657
Full methodology: sources and methodology. Last reviewed 20 October 2026.