Cat Calorie Calculator

How cat calorie needs are calculated

The standard way to estimate a cat's daily calories uses two numbers: the resting energy requirement (RER) and the maintenance energy requirement (MER). RER is what a cat burns at complete rest. MER is what she burns with normal activity, and it is RER times a life stage factor. The AAHA: feeding plans for healthy appropriate weight cats and dogs walks through the same formula, and Tufts Petfoodology: how much should I feed my dog or cat from Tufts uses the same RER and MER approach to recommend a starting point.

The formulas:

RER = 70 x (body weight in kg)^0.75

MER = RER x life stage factor

Common factors for cats:

• Kitten under 4 months: 2.5
• Kitten 4 to 12 months: 2.0
• Adult intact (not spayed or neutered): 1.4
• Adult neutered or spayed: 1.2
• Weight loss: 0.8
• Senior, healthy: 1.1
• Pregnant: 1.6 to 2.0
• Lactating: 2.0 to 3.0

Worked examples

Worked example: a 10 pound neutered adult cat

• Body weight: 10 lb = 4.54 kg
• RER: 70 x 4.54^0.75 = 217.6 kcal
• Factor: 1.2 (adult neutered)
• MER: 217.6 x 1.2 = 261.1, shown as 261 kcal/day
• Food (90 percent): 235 kcal
• Treats (10 percent): 26 kcal

For a 380 kcal per cup dry food, 235 kcal is about 0.6 cup a day, split into two or three meals. For a 3 ounce can of wet food at 85 kcal, 235 kcal is about 2.8 cans a day. Most owners mix the two, which is fine.

Worked example: a 6 month old kitten

A 6 month old kitten at 6 pounds (2.72 kg):

• RER: 70 x 2.72^0.75 = 148.3 kcal
• Factor: 2.0 (kitten 4 to 12 months)
• MER: 148.3 x 2.0 = 296.7, shown as 297 kcal/day
• Food (90 percent): 267 kcal
• Treats (10 percent): 30 kcal

Feed a labeled-for-growth kitten food and split the meals into three or four a day. Kittens burn energy fast and cannot take in enough at one meal to cover a whole day.

Calorie needs by life stage

Calorie needs by life stage (10 pound cat as the example)

The numbers assume a 10 pound cat at healthy weight. Larger or smaller cats scale by body weight to the 0.75 power, which is what the calculator does on the form above.

Translating calories into food

How to translate calories into actual food

• Dry food (kibble). Most dry foods run 350 to 450 kcal per cup. Divide the daily food calories by the kcal per cup on the bag. A 261 kcal MER on a 380 kcal per cup food is about 2/3 cup a day. Use a measuring cup, not a coffee mug.
• Wet food (cans or pouches). A 3 ounce can has 70 to 100 kcal. A 5.5 ounce can has 150 to 200 kcal. Divide daily food calories by the kcal on the label. Most cats do best on 2 to 3 small wet meals a day.
• Mixed feeding. Half wet, half dry is a common middle ground. Work out the wet calories first, then top up with dry to hit the total. Or feed wet in meals and use a small amount of dry for grazing.
• Treats. No more than 10 percent of the daily total per the Tufts Petfoodology and AAHA guidance. For a 261 kcal cat, 26 kcal of treats is about 4 to 5 small training treats, or a tablespoon of plain cooked chicken, or half a teaspoon of plain canned pumpkin.

Recheck and adjust

Recheck the numbers every few weeks

Cats adjust to a calorie level within 2 to 4 weeks. Weigh the cat at the same time of day, once a week, on the same scale, and write it down. A healthy adult at maintenance stays within half a pound month to month. A cat on a weight loss plan should drop 1 to 2 percent of body weight per week, which is faster than for dogs and a sign the plan is working. A cat that should be gaining stays flat or drops weight, the calorie level needs to go up.

The Merck Veterinary Manual: dog and cat foods covers the broader topic of cat and dog food labels, including how to read the calorie content statement that every AAFCO-complete food must carry.

Reading a cat food label

Reading a cat food label

Every bag or can of complete and balanced cat food sold in the US has a calorie content statement in two units, kcal per kg of food and kcal per familiar household measure (cup or can). The Merck Veterinary Manual and AAHA both rely on this number for daily portions. The label also has to carry an AAFCO nutritional adequacy statement that names the life stage the food is tested for (growth, maintenance, gestation and lactation, or 'all life stages'). Treats and snacks are not required to carry the adequacy statement, which is one of the reasons they should stay under 10 percent of the daily intake.

Three things on the label are easy to misread:

• 'With' versus 'dinner' versus 'flavor'. Per AAFCO labeling, 'beef' means at least 70 percent beef, 'beef dinner' means at least 10 percent, 'with beef' means at least 3 percent, and 'beef flavor' means only enough to taste. The first ingredient on the list is the most abundant by weight, but the marketing name is the legal minimum.
• Guaranteed analysis is on an as-fed basis. A dry food at 10 percent moisture and a wet food at 80 percent moisture are not directly comparable. For a real comparison, the AAHA feeding plans resource walks through the dry-matter calculation.
• Feeding guides on the bag are not personalized. AAFCO does not standardize the feeding guide, and bag recommendations often overfeed. Use the bag kcal per cup, plug it into the calculator above, and check the cat's weight monthly.

Common calorie myths for cats

Common calorie myths for cats

• 'Indoor cats do not need as much food.' Indoor cats need fewer calories than outdoor cats, but the difference is small, and it is captured by the 1.2 factor for adult neutered cats. The bigger swing comes from spay or neuter status.
• 'Cats can self-regulate on free-choice dry food.' Most adult cats cannot. Neutered adults in particular tend to overeat, which is the main reason the AAHA nutrition guidelines put them on the 1.2 factor, lower than intact adults.
• 'A little extra weight is fine on a cat.' A 10 pound cat at a healthy 9 to 10 pounds is normal. An 11 pound cat is overweight, and a 12 to 13 pound cat is obese. The weight loss plan factor of 0.8 is for the cat's target weight, not the current weight, which is the main lever for getting an overweight cat back to a healthy range.
• 'Treats do not count toward calories.' They do. WSAVA's table of common foods shows that a 1 oz cube of cheddar is 120 kcal, which is about half a day's calories for a small adult cat. The dog-treat calculator has the same 10 percent rule applied to dogs.
• 'Wet food is more fattening than dry food.' Per calorie, wet and dry foods are close. A 3 oz can of wet food and a third cup of dry food both run around 80 to 100 kcal. Wet food is more satiating per calorie because of the water content, which is one reason vets often suggest it for weight loss cats.