Tool 59/59·Pet Nutrition
Estimate how many calories your cat needs each day from its weight and life stage, then turn it into cups of dry food and cans of wet food.
Life stage or situation
Food calories (optional)
Share of calories from wet food
Find kcal per cup or can under “Calorie Content” on the label. 0% means dry food only, 100% wet food only.
Readout
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Enter your cat's weight
Add a weight and pick a life stage to see daily calories, portions and the treat allowance.
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Vets estimate a cat's energy needs in two steps. The resting energy requirement (RER) is the calories a cat burns at rest in a comfortable room. A life-stage factor then scales it to the maintenance energy requirement (MER), the calories for a normal day. Cat food calories are ordinary kilocalories, the same unit explained in what calories are.
How We Calculate It
RER = 70 x (body weight in kg)^0.75 and MER = RER x life-stage factor, with the feline factors from the 2021 AAHA Nutrition and Weight Management Guidelines. Where the guidelines give a range, the headline number is its midpoint and the range is shown under it.
Take a 10 lb neutered indoor cat. 10 lb is 4.54 kg, and 4.54 raised to the power 0.75 is about 3.11. Multiply by 70 and the RER is about 218 kcal a day. A neutered adult uses 1.2–1.4, which gives about 261–305 kcal a day. If that cat mostly sleeps and puts on weight easily, the inactive factor of 1.0 brings it back to about 218 kcal. Same cat, roughly 40% apart: that is why the body condition check below matters.
| Cat | Factor (x RER) | Note |
|---|---|---|
| Kitten (growth) | 2.5 | Merck: or feed free choice |
| Neutered adult | 1.2–1.4 | Merck uses 1.2 |
| Intact adult | 1.4–1.6 | Merck uses 1.4 |
| Inactive or obesity-prone | 1.0 | AAHA and Merck agree |
| Weight loss | 0.8 | RER at target weight |
| Pregnancy | 1.6–2.0 | Vet plan needed |
| Nursing | 2.0–6.0 | Rises with litter size and week |
Sources: AAHA 2021, Box 1; Merck Veterinary Manual. AAHA adds that indoor and sedentary pets may need less than these factors suggest.
Neither source gives a separate senior factor. Senior cats are 10 years and older under the AAHA/AAFP Feline Life Stage Guidelines, and the AAHA nutrition guidelines note that older cats digest fat, protein and energy less well and may need more calories, not fewer. The calculator starts seniors at the neutered-adult range; weight that keeps dropping is a reason to see the vet.
Wet and dry cat food differ mostly in water. Dry food is about 10% water, while canned food holds 68–78% water, according to the Merck Veterinary Manual. So a can has far fewer calories per gram than a cup of kibble, and comparing them by weight or volume misleads. Compare on calories instead.
The number to use is the Calorie Content statement. Under AAFCO rules, it gives kilocalories per kilogram of food as fed and per familiar unit, such as a cup or a can, and sits near the guaranteed analysis. Enter the kcal per cup and per can or pouch above, pick how much of the day comes from wet food, and the calculator splits the calories between the two.
Treats count too. The AAHA guidelines keep treats and other extras to 10% or less of daily calories, so the complete food still supplies the nutrients a cat needs. That is why the result shows a treat allowance and a smaller main-food portion.
Formulas give a starting point; the cat tells you if it is right. The WSAVA 9-point body condition score rates 5 as ideal: ribs felt under a slight fat covering, a waist behind the ribs and a minimal belly fat pad. At 7 the ribs are hard to feel and the belly rounds; at 9 there is no waist and heavy fat over the back, face and limbs. The chart notes that a 6 may be acceptable in some older cats.
Score your cat every few weeks. If the score climbs, trim the portion a little; if the ribs and spine grow sharp, feed a little more. A review in the Journal of Feline Medicine and Surgery calls for a nutritional assessment of every cat at every visit, with body and muscle condition checked separately.
Cats handle hunger badly. When an overweight cat stops eating, fat floods the liver faster than it can be processed. This is hepatic lipidosis, or fatty liver. Cornell's Feline Health Center says it is much more common in obese cats and likely to be fatal if not treated promptly. The Merck Veterinary Manual names anorexia or food deprivation in overconditioned cats as the setting for the disease.
So weight loss has to be slow. AAHA bases the calculation on the target weight and uses 0.8 x RER; a review in Veterinary Medicine: Research and Reports recommends losing 0.5–2% of body weight a week and warns that energy restriction can lead to hepatic lipidosis. A 14 lb cat with an 11 lb target gets about 187 kcal a day and should lose roughly 1–4.5 oz a week. Because that is below RER, AAHA advises a therapeutic weight-loss food fortified with nutrients. Never cut food abruptly, and call the vet if your cat skips meals.
Have a dog as well? Use the dog calorie calculator, or browse all free tools.
01
Start with the resting energy requirement, 70 x (body weight in kg)^0.75, then multiply by a life-stage factor. Under the 2021 AAHA guidelines a neutered adult uses 1.2–1.4, so a 10 lb (4.5 kg) neutered cat needs about 260–305 kcal a day. If the same cat is an inactive indoor cat that gains weight easily, the factor is 1.0, or about 218 kcal. Treat the number as a starting point and adjust by body condition.
02
Divide the cat's daily calories by the calories in one can or pouch. If a cat needs 260 kcal and the label says 80 kcal per can, that is about 3.25 cans a day on wet food alone. If you also feed dry food, decide what share of the calories each food supplies, then divide each share by that food's kcal per can or per cup.
03
AAHA uses 0.8 x RER calculated at the cat's ideal or target weight, not its current weight. For a 14 lb cat with an 11 lb target, that is about 187 kcal a day. Aim for a loss of 0.5–2% of body weight a week, weigh the cat every few weeks and work with your vet, because cats that lose weight too fast or stop eating risk hepatic lipidosis.
04
Kittens need about 2.5 x RER at their current weight, according to both the AAHA guidelines and the Merck Veterinary Manual, which also notes that kittens can be fed free choice. A 3 lb kitten works out to about 220 kcal a day. Because kittens gain weight every week, recalculate often and feed a food labelled for growth.
05
Yes. An overweight cat that stops eating or eats far too little can develop hepatic lipidosis, or fatty liver, which Cornell's Feline Health Center describes as likely to be fatal if not treated promptly. A cat that refuses food should see a vet, and any diet should cut calories gradually rather than all at once.