Pet Calorie Calculator — Daily Calories for Dogs & Cats (RER/MER)
Estimate your dog or cat’s daily calorie needs from weight and life stage (RER = 70 × kg^0.75 × factor), plus grams of food per day from the label’s kcal/100 g. A general guide — confirm with your vet.
🔒 Runs entirely in your browser. Your input and output are never sent to a server or stored — fully private.
RER = 70 × (weight in kg)^0.75; daily calories = RER × life-stage factor. Enter your food’s kcal/100 g (from the label) to get grams per day. Click any value to copy.
About this tool
Guesswork at the food bowl is the fastest route to an overweight pet. This calculator estimates the daily calorie needs of dogs and cats with the standard veterinary method: the resting energy requirement, RER = 70 × (body weight in kg)^0.75, multiplied by a life-stage factor for growth, neuter status, activity level or weight management. A food-grams helper then turns the kilocalorie target into grams per day using the calorie density printed on your pet food label. Everything is calculated locally in your browser, and no details about your pet are stored or transmitted.
Frequently asked questions
How is the daily calorie figure calculated?
It starts from the resting energy requirement, RER = 70 × (body weight in kg)^0.75 — the calories a pet burns at complete rest. That is then multiplied by a life-stage factor: a typical neutered adult dog gets about 1.6 × RER and an intact adult 1.8, while a neutered adult cat gets about 1.2 and kittens or puppies 2 to 3 because growth is expensive. Weight-loss plans use factors at or below 1.0 × RER based on ideal weight. The whole calculation runs locally in your browser.
How do I turn the calorie target into grams of food?
Find the metabolizable energy on your pet food label — usually printed as kcal/kg or kcal per cup, and around 3,500–4,000 kcal/kg for typical dry food. Enter it in the grams helper and the tool divides the daily calorie target by that density: a 400 kcal day on 3,800 kcal/kg food means about 105 g. Remember that treats count too — the common advice is to keep them under 10% of daily calories and subtract them from the main meals rather than adding them on top.
Can I rely on this instead of asking a vet, especially for weight loss?
No — treat the output as a general starting point, not veterinary advice. Real energy needs can differ from the formula by 50% in either direction depending on breed, metabolism, body condition and health, so weigh your pet regularly and adjust portions gradually. Any weight-loss plan in particular should be designed with a vet: losing weight too fast is dangerous, and in cats it can trigger hepatic lipidosis, a life-threatening liver condition. Confirm targets, food choice and pace with your veterinarian before changing the diet.