Pet Calorie Calculator
A starting estimate of the calories a dog or cat needs a day: resting energy from body weight, times a life-stage factor.
Result…
How it's calculated
RER (kcal a day) = 70 × body weight in kg^0.75 Daily energy = RER × life-stage factor Food a day = daily energy ÷ calories per 100 g × 100 (or ÷ kcal per cup)
Vets estimate a pet's daily calories in two steps. The resting energy requirement (RER) is 70 × weight in kg to the power 0.75, the energy used at rest. It is multiplied by a factor for life stage and lifestyle. The factors here are the ones in the Merck Veterinary Manual's table of maintenance energy requirements: adult dogs 1.8 (not neutered), 1.6 (neutered) or 1.4 (prone to obesity), puppies 3 under 4 months and 2 after; adult cats 1.4, 1.2 or 1, kittens 2.5. The manual stresses that any such figure is only a starting point to adjust from. Pick "A factor from my vet" to use a different one, for example for weight loss, which your vet should plan. Weights in pounds are converted at 0.45359237 kg per lb.
Your numbers, step by step
About the Pet Calorie calculator
This pet calorie calculator gives a starting estimate of how many calories a dog or cat needs in a day. It uses the two-step method vets use: first the resting energy requirement (RER), which is 70 × body weight in kg to the power 0.75, then a factor for life stage and lifestyle, such as neutered adult, puppy or kitten. The factors come from the maintenance energy table in the Merck Veterinary Manual, which notes that any such figure is only a starting point to adjust from. Enter the weight in kg or lb, and optionally the calories on the food's label per 100 g, per kg or per cup to see how much to feed. The steps show each part of the sum. It is not veterinary advice: your vet knows your pet's health and can give a different factor.
How to use it
- Choose “Dog” or “Cat” under “Pet”, and kg or lb under “Weight in”.
- Enter the “Body weight”.
- Pick the “Life stage”, or “A factor from my vet” and type the “Factor” your vet gave you.
- To see an amount to feed, choose how the label gives “Food energy (optional)” and enter the “Calories in the food”.
- Read the calories a day, the resting energy and the amount of food, then weigh your pet regularly and adjust.
Worked example
A neutered adult dog weighing 15 kg has an RER of 70 × 15^0.75 = 533.5 kcal a day. Times the neutered-adult factor of 1.6, that is about 854 kcal a day. With a food whose label says 380 kcal per cup, that is 854 ÷ 380 = about 2.25 cups a day. A neutered cat of 10 lb (4.54 kg) has an RER of 217.6 kcal; × 1.2 gives about 261 kcal a day, or about 65 g (2.3 oz) of a food with 400 kcal per 100 g.
Updated
Questions people ask
How do I calculate how many calories my dog needs?
Work out the resting energy requirement, RER = 70 × weight in kg^0.75, then multiply by a life-stage factor. The Merck Veterinary Manual gives 1.6 for a neutered adult dog and 1.8 for an intact one.
How many calories should a cat eat a day?
Use the same RER formula with a cat factor: 1.2 for a neutered adult, 1.4 for an intact adult, 1 for a cat prone to obesity and 2.5 for a kitten. A 4 kg neutered cat comes to about 238 kcal a day.
What is RER for dogs and cats?
RER, the resting energy requirement, is the energy an animal uses at rest in a comfortable environment. It is calculated as 70 × body weight in kg raised to the power 0.75, and the daily need is RER times a factor. Choose lb to enter pounds, or convert first with the weight converter.
Should I use my pet's current weight or ideal weight?
For a pet at a healthy weight, use its current weight. For weight loss, vets usually plan from a target weight and a lower factor, so ask your vet for the weight and factor to use and enter them as “A factor from my vet”.
Do treats count toward the daily calories?
Yes. Treats, chews and table scraps are part of the daily total, so feed less of the main food to make room for them.
How accurate is a pet calorie estimate?
It is a starting point only. Needs differ between animals of the same weight with breed, activity, age and health. Weigh your pet every few weeks, adjust the amount, and ask your vet, especially for puppies, kittens, pregnant or ill animals.