How the cat food calculator works
We calculate resting energy requirement with 70 × body weight in kg^0.75, then apply a life-stage factor. A neutered adult cat typically needs about 1.2 × RER, while a growing kitten can need 2-2.5 × RER. Dividing by the food’s calories per cup turns the target into a portion.
The result is an estimate for a healthy cat. Individual metabolism, indoor versus outdoor access, and body condition can shift the number by 20% or more.
Dry food, wet food and free feeding
Cats are obligate carnivores with a low thirst drive, so wet food has real advantages for hydration and urinary health. A mixed diet is common: use the can label for its calories and subtract that from the daily total before measuring dry food.
Free feeding dry food works for some kittens and very active cats, but it makes weight control difficult. If your cat is overweight, measure meals and feed at set times rather than topping up the bowl.
- Most adult cats do well with two or three measured meals a day.
- Wet food left out should be removed after about 30 minutes.
- Use a kitchen scale for portions if you can; cups vary by food shape.
- Never put a cat on a severe diet without veterinary supervision.
When to ask your vet
Cats that lose weight despite eating, stop eating for more than 24 hours, or show sudden changes in thirst and urination need prompt veterinary care. Overweight cats are at higher risk of diabetes and arthritis, but rapid weight loss can cause a dangerous liver condition.