Frequently asked questions

Yes — completely free, no account needed, and no ads. We believe every pet owner deserves access to accurate nutrition science without a paywall or subscription.

The formulas are the same ones used by veterinary nutritionists worldwide. That said, all calculators produce estimates — individual pets can vary by up to ±20% due to breed, body composition, metabolism, and health. Treat our result as your starting point and adjust based on your pet's weight trend over 4–6 weeks. If they're gaining weight, reduce by 10–15%. If losing unintentionally, increase slightly.

Recalculate whenever your pet's weight changes noticeably (more than about 5%), or after a major life change — getting spayed or neutered, moving from outdoors to indoors, entering senior years, or starting a weight loss program. For puppies and kittens, recalculate every month since they grow so fast.

Yes, for most pets. Dogs do well with 2 meals per day. Cats prefer 2–3 smaller meals. Small mammals like rabbits and guinea pigs can have food available most of the time (especially hay). Fish should be fed once or twice daily in small amounts. Splitting helps avoid bloating, keeps energy levels stable, and is better for digestion than one large meal.

Neutering (for males) and spaying (for females) is a routine veterinary surgery that stops your pet from being able to reproduce. Most vets recommend it for pet dogs and cats. After the procedure, your pet's metabolism slows slightly — typically needing about 20–25% fewer calories than before. This is why it's a specific option in the calculator.

Choose "Couch potato — very low activity" if your dog is genuinely sedentary, regardless of neuter status. The lifestyle description is the most important factor. If they're moderately active and not neutered, choose "Not neutered / not spayed, normal activity." The descriptions are written to capture real-life situations, so just pick the one that sounds most like your pet's actual day.

If they spend more time inside than out and are neutered / spayed, choose "Neutered or spayed adult." If they roam outdoors regularly for hours each day and are not desexed, choose "Not neutered / not spayed, goes outdoors." When in between, it's fine to pick either — our results are estimates and the difference between adjacent multipliers is small.

Use our "Choose from list" option in Step 4 — it has typical calorie values for the most common food types. If you want more precision, look for a section called "Calorie Content" or "Metabolizable Energy (ME)" on the back or side panel of the bag or can. It's usually near the ingredients list and says something like "3,500 kcal/kg" or "350 kcal/cup." If it's only on the manufacturer's website, that works too.

kcal/kg measures calories by weight — this is the most accurate method because weight doesn't depend on kibble size or how packed your cup is. kcal/cup measures calories by volume using a standard 8oz measuring cup. The problem with cups is that different kibbles have different densities, so "1 cup" of large breed kibble weighs differently than "1 cup" of small breed kibble. Whenever possible, weigh your pet's food in grams — it's more accurate than scooping.

Run the calculator once to get your pet's total daily calorie target. Then decide what proportion comes from each food type (e.g. 50% dry, 50% wet). For each food, divide the calorie portion by that food's calorie density to get the gram amount. For example: if your cat needs 200 kcal/day, you want 100 kcal from dry (at 3,600 kcal/kg = 27.8g dry) and 100 kcal from wet (at 1,100 kcal/kg = 90.9g wet).

Yes — treats are real calories and should count toward the daily total. Vets recommend treats make up no more than 10% of total daily calories. If you give treats regularly, subtract their calorie value from the daily food portion. Many treat bags now list kcal per treat — check the packaging.

Fish are cold-blooded (ectothermic) — their body temperature matches the water, so they don't burn calories keeping warm the way mammals do. This makes their energy needs far lower and harder to measure in calories. Aquarium science instead uses the "percentage of body weight" method: feeding a set percentage of the fish's weight in food daily. This is the same approach used by professional aquaculturists and is recommended by the University of Florida's fish nutrition guidelines.

You don't need to weigh them individually. Use reference sizes: a betta is roughly 3–5g, a neon tetra 1–2g, an adult goldfish 100–200g, a large cichlid 50–150g. For a tank with multiple fish, add up estimates for all of them. The percentage-based calculation is forgiving — small estimation errors don't significantly change the result.

Uneaten fish food sinks and decomposes, releasing ammonia into the water. Ammonia is toxic to fish even in small amounts and is the most common cause of fish death in home aquariums. The "2-minute rule" ensures no food is left behind. If there's always food left after 2 minutes, you're overfeeding. This is far more important for fish health than precise calorie counting.

PetKcal provides a healthy baseline for typical animals. Pets with kidney disease, diabetes, pancreatitis, cancer, hyperthyroidism, heart disease, or post-surgical recovery needs should have their diet managed by a veterinary nutritionist. Our results can give you a useful reference point for conversations with your vet, but don't replace specialist guidance for medically complex pets.

Feeding guides on pet food bags are printed for "average" animals of a given weight and tend to be on the generous side (since selling more food benefits the manufacturer). Our calculator personalises the estimate based on your pet's actual lifestyle. In many cases, the true requirement is 10–20% lower than what the bag suggests — especially for neutered, indoor, or less active pets. Use your pet's body condition (can you feel their ribs easily? is there a waist visible from above?) as your guide.

Select the "weight loss" or lowest-activity lifestyle option for your species. The resulting calorie target is intentionally reduced. Introduce the new portion gradually over 1–2 weeks (don't suddenly cut food by 30% — it's stressful for the animal). Aim for slow, steady weight loss — about 1–2% of body weight per month is a healthy rate. Always consult your vet for a formal weight loss plan, especially for cats, where rapid weight loss can cause a serious liver condition called hepatic lipidosis.