How much should I feed my dog or cat?

The RER and MER formulas vets use

Veterinary nutrition starts with the resting energy requirement (RER), the calories a pet needs at rest in a comfortable environment: RER = 70 × (body weight in kg)0.75. Raising weight to the power of 0.75 reflects the fact that small animals burn more energy per kilogram than large ones. The maintenance energy requirement (MER) then multiplies RER by a factor for life stage and activity. Commonly published starting factors are about 1.6 for a neutered adult dog, 1.8 for an intact adult dog, 3.0 for puppies under four months and 2.0 for older puppies, and about 1.2 for a neutered adult cat, 1.4 for an intact cat and 2.5 for kittens. These are averages; individual pets can need 20–30% more or less.

From calories to grams and cups

Pet food labels list the energy content as kcal per kg and often kcal per cup or per can. Divide the daily calories by the kcal per kg and multiply by 1,000 to get grams. For example, a 12 kg neutered adult dog has an RER of about 451 kcal and an MER of about 722 kcal. With a dry food of 3,700 kcal/kg, that is about 195 g a day, or roughly 98 g per meal over two meals. A 4 kg neutered indoor cat needs about 238 kcal a day; with a dry food of 3,900 kcal/kg that is about 61 g. Weighing food on a kitchen scale is far more accurate than using a scoop, because "one cup" of kibble can vary by 20% or more.

Weight loss: use the ideal weight

Over half of pet dogs and cats in many countries are estimated to be overweight. For weight loss, vets typically feed about 1.0 × RER for dogs and 0.8 × RER for cats, calculated at the target (ideal) weight, not the current weight. Choose "weight loss" and enter the ideal weight your vet suggests. A safe rate is usually around 1–2% of body weight per week for dogs and about 0.5–1% for cats. Cats must never be starved or put on very aggressive diets, because rapid weight loss can trigger a serious liver condition called hepatic lipidosis.

Body condition score: is your pet the right weight?

Vets use a 9-point body condition score. At the ideal score (4–5 out of 9) you can feel the ribs easily under a thin layer of fat without pressing hard, see a waist behind the ribs from above, and see a slight tummy tuck from the side. If you cannot feel the ribs, your pet is likely overweight; if ribs, spine and hip bones are clearly visible, it may be underweight. Weigh your pet every two to four weeks and adjust portions by about 10% if the weight is moving the wrong way.

Don't forget treats and extras

Treats, chews, table scraps and training rewards all count. A common guideline is that treats should provide no more than 10% of daily calories. For the 12 kg dog above, that is about 70 kcal, roughly one medium dental chew. If you give more treats, reduce the main meal.

Puppies, kittens and seniors

• Puppies need more calories per kilogram and several meals a day; large-breed puppies should grow slowly on a large-breed puppy food to protect their joints.
• Kittens grow fast and usually eat three to four small meals a day.
• Senior pets often need fewer calories because they are less active, though very old cats sometimes need more as digestion becomes less efficient.

When to see your vet

Sudden weight loss or gain, increased thirst, vomiting, or a change in appetite can signal illness, not just a feeding problem. Pets with kidney disease, diabetes, pancreatitis or allergies need diets planned by a vet. This calculator gives a starting point only.

Wet food, mixed feeding and homemade diets

Wet foods contain about 70–80% water, so they have far fewer calories per gram than kibble, often 800–1,200 kcal/kg. If you mix wet and dry food, split the daily calories between them: for example, give 30% of the calories as wet food and 70% as dry, and calculate each portion separately with its own kcal value. Homemade diets need careful balancing of calcium, vitamins and fatty acids; ask a veterinary nutritionist for a recipe rather than guessing.

More feeding and care guides on Cute Home Pet World.

Frequently asked questions