Estimate how many calories your dog or cat needs each day from its weight and life stage, then turn that into cups or grams of your food.
Resting energy requirement (RER) is 70 × bodyweight in kg to the power 0.75 — the calories a pet burns at rest. Daily energy requirement (DER) multiplies RER by a life-stage factor (e.g. 1.6 for a neutered adult dog, 1.2 for a neutered cat).
We then divide DER by your food’s energy density to get a daily portion, and split that across your chosen number of meals. Always adjust to keep your pet at a healthy body condition.
Bag guides are broad ranges. A calorie estimate from your pet’s actual weight and life stage is usually more precise — but monitor body condition and adjust.
Look for the metabolisable energy on the label — often given as kcal per cup (US) or kcal per 100 g (EU). Enter whichever your bag shows.
No. It is an informational estimate. For weight loss, illness, pregnancy or growth, confirm the plan with your veterinarian.
This calculator works out the daily calorie needs of a dog or cat using the Resting Energy Requirement (RER) and the Daily Energy Requirement (DER). RER is the baseline energy the animal needs at rest; DER scales that up by a life-stage factor to account for growth, activity, or reproductive status. The result is then converted to a practical daily portion and a per-meal amount based on your food's energy density.
The headline figure is the DER in kcal/day — the total calories your pet needs each day. Below it you will see a daily portion (in cups or grams depending on your selection) and the amount per meal. The horizontal bar shows how the DER is split: the darker segment is the resting baseline (RER) and the lighter segment is the extra energy the pet requires above that baseline due to its life stage. These figures are estimates based on population-average factors; individual needs can differ, so treat the output as a starting point rather than a substitute for veterinary advice.
A 20 kg neutered adult dog; food contains 350 kcal per cup; fed 2 times per day.
RER = 70 × 20^0.75 = 662 kcal/day. DER = 662 × 1.6 (neutered adult factor) = 1,059 kcal/day. Daily portion = 1,059 ÷ 350 = 3.03 cups; each meal = 1.51 cups.
RER (Resting Energy Requirement) is the energy a healthy animal uses while resting in a thermo-neutral environment — essentially the calories needed to sustain basic body functions. DER (Daily Energy Requirement) multiplies RER by a life-stage factor (such as 1.6 for a neutered adult dog) to account for activity, growth, pregnancy, or weight-management goals. You feed to the DER, not the RER alone.
The factor can range from 0.8 (weight-loss cat) to 3.0 (young puppy or highly active working dog), meaning a very active dog of the same weight can need nearly four times as many calories as a cat on a restricted diet. Choosing the wrong stage is the most common reason a pet is underfed or overfed, so match it carefully to your pet's current situation.
Divide the DER by the energy density of your food. For dry kibble, the bag will typically list kcal per cup or kcal per 100 g (often 300–450 kcal per cup). For wet food, use kcal per 100 g from the can. Enter that density in the food field and choose the matching unit; the calculator does the division for you.
Yes — select "Young puppy (0–4 months)" or "Older puppy" for dogs, or "Kitten" for cats. These stages carry higher factors (2.5–3.0) to support rapid growth. Because young animals can change quickly, re-check the portion every few weeks as your pet gains weight.
These estimates are a reliable starting point based on the Merck Veterinary Manual and WSAVA guidelines, but individual metabolism, breed, health status, and food digestibility all vary. Monitor body condition (you should be able to feel but not see the ribs) and adjust portions by 10–15% if your pet is gaining or losing weight unexpectedly. Always consult a veterinarian for specific dietary advice.
The calculation follows the metabolic energy framework published in the Merck Veterinary Manual and the WSAVA Global Nutrition Guidelines. Step 1: compute RER = 70 × (body weight in kg)^0.75. The exponent 0.75 is the metabolic body weight scaling factor derived from interspecies studies by Kleiber and validated by the National Academies (NRC 2006). Step 2: multiply RER by the appropriate life-stage factor to obtain DER. Dog factors range from 1.0 (weight loss) to 3.0 (young puppy/highly active); cat factors range from 0.8 (weight loss) to 2.5 (kitten). Step 3: convert DER to a portion by dividing by the food's energy density — either kcal per cup (for kibble measured by volume) or kcal per 100 g (for food measured by weight), then multiplying by 100 in the latter case. Per-meal amount is portionPerDay divided by the number of meals.
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