Enter your pet's weight and life stage to estimate daily calorie needs using a standard veterinary nutrition formula — add your food's calorie density from the bag and it'll also work out a suggested daily feeding amount in grams.
RER stands for Resting Energy Requirement — in plain terms, it's how many calories an animal would burn in a day if it did nothing but lie around resting, just keeping its heart beating, lungs breathing, body temperature stable, and organs running. It's the starting point for any daily feeding calculation, because no matter how active your pet is on a given day, this "basal metabolism" calorie floor always has to be met. This tool uses RER = 70 × weight(kg)^0.75, one of the most widely used formulas in veterinary nutrition, applicable to dogs and cats over roughly 2 kg. From RER, you multiply by a "factor" determined by life stage to get the true daily total — the Maintenance Energy Requirement (MER) — because activity, growth, and spay/neuter status all push actual needs above that resting baseline.
If daily calorie needs scaled perfectly with weight (i.e., weight to the power of 1), a 20 kg dog would need exactly double the calories of a 10 kg dog — but that's not what's actually observed. Energy expenditure correlates more closely with an animal's metabolically active tissue mass than with raw body weight, and larger animals tend to carry proportionally more low-energy-cost tissue like fat and bone; they also have a smaller surface-area-to-volume ratio, which changes heat-loss dynamics. Together, these factors mean calorie needs rise more slowly than a straight 1-to-1 ratio with weight would suggest. The 0.75 exponent (a version of what's known in biology as "metabolic body size" or Kleiber's Law) corrects for this non-linear relationship, producing a much closer match to how animals actually burn energy — which is exactly why veterinary nutritionists widely use this formula instead of a simple "weight × fixed multiplier."
Spay/neuter surgery sharply reduces the sex hormones that normally stimulate metabolic rate and activity level to some degree. Research consistently shows that resting metabolic rate drops after spay/neuter, and behavioral changes post-surgery (lower activity, sometimes a modest appetite increase) compound the effect — feeding at pre-surgery calorie levels after the fact is a common path to unwanted weight gain. That's why this tool sets the "spayed/neutered adult" factor (1.6) lower than "intact adult" (1.8), reflecting the generally lower energy needs after the procedure, and it's a good reminder to watch portion sizes more closely once a pet has been spayed or neutered.
Take a spayed adult dog weighing 12 kg. First, RER: 12 to the power of 0.75 is roughly 6.45, times 70 gives RER ≈ 70 × 6.45 ≈ 451.5 kcal. Then apply the "spayed/neutered adult" factor of 1.6: MER = 451.5 × 1.6 ≈ 722 kcal — that's roughly the total daily calories this dog needs. If their food bag states "350 kcal per 100g," you can further work out the suggested feeding amount: (722 ÷ 350) × 100 ≈ 206 grams per day, ideally split across 2–3 meals rather than fed all at once.
No. This tool uses a general veterinary nutrition formula that doesn't account for your pet's actual exam results, medical history, or specific constitution — it's only a reasonable starting estimate. If your pet has a chronic condition, special dietary needs, or their weight hasn't stayed in a healthy range, always defer to your vet's actual evaluation and any prescribed diet.
No. RER/MER is a general estimation formula meant for healthy pets without special medical conditions — it makes no adjustment for kidney disease, diabetes, heart disease, or other conditions requiring specific dietary management. Calorie and nutrient needs for pets with chronic conditions often differ substantially from the general formula, and that situation always calls for individualized assessment by a vet using a prescription diet, not just this tool's number.
Its accuracy depends entirely on whether the "food calorie density" you entered is correct. Calorie density per 100g varies significantly between brands and formulas — if the number you enter doesn't match what's actually printed on your food bag, the resulting gram estimate will be off too. Always check the calorie density printed on the specific bag you're currently using before entering it, rather than relying on memory or a number from a different product.
Both states demand meaningfully more energy than a typical adult: growing puppies and kittens need extra calories to fuel rapid development, while nursing mothers or high-intensity working dogs need extra calories for milk production or heavy physical exertion — the two happen to land in a similar multiplier range, so this tool simplifies them to one shared factor. Worth noting: actual needs for nursing or working dogs can go well above 2.5× (peak lactation can even exceed 3×), so this factor is only a baseline — that situation is a good one to bring directly to your vet for fine-tuning.
No. All calculations run entirely in your browser — there's no code on this page that sends weight, life stage, or food calorie data to a server. Refreshing the page resets every field, and no history is kept anywhere.