Cat Food Calculator

How much to feed your cat, by calories and cups — based on weight and life stage. Updated for 2026.

Last reviewed September 2026 · Free · Nothing you enter is stored

How much should I feed my cat?

By calories, and then by weighing the food — not by the cup, and not by the chart on the bag. This calculator finds your cat's Resting Energy Requirement, applies a life-stage factor to get the Maintenance Energy Requirement, and divides by your food's calorie density to produce a daily portion.

Cats deserve a more careful treatment than dogs here, for two reasons that most feeding calculators ignore. The published uncertainty is wider, and the way energy needs change with age runs in the opposite direction from what almost everyone is told.

Cats do not scale the way dogs do

The familiar equation, RER = 70 × (kg)^0.75, is shared across species and is what this calculator uses. But WSAVA's own owner-facing charts do not use it for cats at all. They apply the NRC 2006 maintenance equations directly, and those use a different exponent: 100 × kg^0.67 for a lean adult cat and 130 × kg^0.40 for an obese-prone one.

That second equation is the striking one. An exponent of 0.40 means a heavier cat's maintenance requirement rises far more slowly with weight than the standard three-quarter scaling predicts — which is a formal way of saying that an overweight cat is not simply a bigger cat, and feeding it as though it were will keep it overweight. For a 3 kg cat the two equations give 209 and 202 kcal; the gap widens considerably as weight rises.

The error band is 50%, not 30%

AAHA's nutritional assessment guidelines put it plainly: population-based energy estimates "can vary by 50% in either direction for cats, and by 30% in either direction for dogs." Fifty per cent in either direction is a wider spread than the entire distance between the life-stage multipliers. A calculated 220 kcal per day means, honestly, somewhere between about 110 and 330.

This is not a reason to ignore the number. It is a reason to treat it as a hypothesis: feed it, re-weigh in two to four weeks, re-score body condition, and adjust by around 10% at a time. Cats are small enough that a 30 g daily error compounds visibly over a season.

Senior cats are the exception nobody mentions

The universal advice that older pets need fewer calories is true for dogs and misleading for cats. AAHA's 2023 senior care guidelines state that maintenance energy requirements decrease in cats up to about age ten, "after which they start to increase" — while noting that published data on age effects in cats are "extremely variable."

The practical consequence is serious. Cats over ten are the group most vulnerable to losing lean muscle mass, and they are also the group most likely to be quietly under-fed by an owner following senior-pet advice written with dogs in mind. If your cat is over ten and losing condition, the answer is more likely to be more food and a veterinary check for hyperthyroidism, kidney disease or diabetes than a smaller portion.

A cup of cat food is not a fixed quantity

A peer-reviewed survey of commercial weight-management diets found dry cat foods ranging from 235 to 480 kcal per cup, a median of 342. The same measured cup can deliver either figure. Canned foods in the same survey ranged from 78 to 172 kcal per can — meaning "one can twice a day" spans more than a factor of two.

Household scooping adds its own error, measured in dogs at anywhere from an 18% underestimate to an 80% overestimate, and worst at small volumes. Small volumes are precisely what cats eat. A kitchen scale and the kcal-per-kilogram figure from the label removes this whole category of error, and for a cat it matters more than it does for a Labrador.

Weight loss in cats is a veterinary procedure, not a diet

Feline weight loss carries a specific risk that canine weight loss does not: a cat in negative energy balance can develop hepatic lipidosis, in which fat mobilised faster than the liver can process it accumulates in liver cells. It can be fatal, and it is precipitated by exactly the kind of abrupt restriction a well-meaning owner might attempt.

AAHA's parameters are a target rate of 0.5–2% of body weight per week and a starting intake of 80% of RER calculated at ideal weight, with restriction below roughly 60% of RER flagged as risking nutritional deficiency. Note that this is ideal weight, not current: the same diet survey found weight-management label directions specifying, at the median, the resting requirement for the cat's current weight — a figure that maintains an overweight cat exactly where it is.

Body condition, and what the 9-point scale means

Weight alone cannot tell you whether a cat is carrying too much fat. The 9-point body condition scale can: 4–5 is ideal, 1–3 under, 6–9 over, with each point above 5 corresponding to roughly 10% overweight. At an ideal 5, the ribs are palpable under a slight fat covering, there is a visible waist behind the ribs, and the abdominal fat pad is minimal. At 7, the ribs are hard to feel, the waist is poorly defined and there is an obvious rounding of the abdomen.

Score the cat rather than trusting the scale, and if it feels like guesswork, have your vet score once and show you what each grade feels like under the hand. Owner self-assessment has been measured as roughly a coin flip, with underestimation the more common error.

Frequently asked questions

Sources: AAHA Nutritional Assessment Guidelines, Weight Management Guidelines and 2023 Senior Care Guidelines; WSAVA Global Nutrition Committee calorie charts (NRC 2006 equations); Merck Veterinary Manual; Linder & Freeman, JAVMA 2010;236(1):74–77. Figures we could not verify from a primary source are not published here.