How Much to Feed Your Dog or Cat: The Calorie Math Behind the Bowl

Most of us learned to feed pets by eyeballing it. One scoop in the morning, one at night, top it up if the bowl looks empty. That habit is how a healthy 10 kg dog quietly becomes a 13 kg dog by next spring. The honest answer to "how much should I feed?" is not a number of cups — it's a number of calories, worked out from your pet's weight and activity, then translated into cups using the calorie density printed on your specific bag of food.

This guide walks through the same two-step formula that vet schools teach: resting energy first, daily energy second, then a conversion to actual portions. You can do the arithmetic by hand, or let the pet food calculator run it and split the result into morning and evening meals.

Step One: Resting Energy (RER)

Resting Energy Requirement is the calories an animal burns just lying still — breathing, pumping blood, holding body temperature. The standard formula is:

RER = 70 × (body weight in kg) ^ 0.75

The 0.75 exponent matters more than the 70. It comes from Kleiber's law (1932), the observation that metabolic rate scales with body weight to the three-quarter power across mammals from mice to elephants. In plain terms: bigger animals burn fewer calories per kilogram than smaller ones. A 10 kg dog needs about 394 kcal at rest. A 30 kg dog — three times heavier — needs about 898 kcal, not 1,182. This is exactly why scaling food linearly by weight overfeeds large dogs and starves small ones.

If your pet's weight is in pounds, divide by 2.205 first. A 22 lb dog is 10 kg.

Step Two: Daily Energy (MER)

Resting calories are only the floor. A real dog walks, plays, regulates temperature in cold weather, and digests food — all of which burns more. To get the Maintenance Energy Requirement (also called DER, daily energy requirement), multiply RER by a factor that reflects the animal's life stage, neuter status, and activity:

Daily calories = RER × activity factor

Typical factors for adult dogs:

Neutered adult, normal activity: 1.6
Intact adult, normal activity: 1.8
High activity (agility, long hikes): 2.0–3.0
Working dog (sled, herding, hunting): 3.0–5.0
Weight loss target: 1.0

Cats run leaner. A neutered indoor cat sits around 1.2, an intact cat around 1.4, and an obese-prone cat on a weight-loss plan drops to 0.8–1.0. Neutering is not a footnote: removing the gonadal hormones cuts resting metabolism by 20–30%, so the same animal needs noticeably less food after surgery than before. Keep filling the old scoop and weight gain within six months is close to guaranteed.

Step Three: Calories to Cups (or Grams)

Calories are the truth, but you serve food in cups and grams. The bridge is the calorie density on the bag, usually labeled "ME" or "calorie content," printed in small type on the side panel.

Daily grams = (daily calories ÷ kcal per 100 g) × 100
Daily cups  = daily calories ÷ kcal per cup

Dry kibble typically runs 340–400 kcal per 100 g; a standard 8 oz measuring cup of kibble holds roughly 300–400 kcal depending on density. Puppy and working formulas push 420–460. Light or weight-management blends drop to 280–320. Wet food is far lower — around 80–100 kcal per 100 g — because it's mostly water, so the gram number for wet food looks alarmingly large and is still correct. Always use the number from your bag; a 20% difference in density is the difference between a lean dog and a chunky one.

A Worked Example: One 10 kg Dog

Say I have a 10 kg neutered adult terrier mix, normal activity, eating a kibble rated 380 kcal per 100 g (about 340 kcal per cup). Here's the full chain:

RER = 70 × 10^0.75 = 70 × 5.62 = 394 kcal
Daily calories = 394 × 1.6 (neutered adult) = 630 kcal
Grams = (630 ÷ 380) × 100 = 166 g per day
Cups = 630 ÷ 340 = about 1.85 cups per day

Split across two meals, that's roughly 83 g — a little under a cup — morning and evening. The treat budget, capped at 10% of daily calories per WSAVA guidance, is 63 kcal, which is about two small biscuits or 20 g of plain cooked chicken. On a training-heavy day, subtract those treat calories from dinner rather than stacking them on top of a full bowl.

That single example shows why the math beats the scoop: the same dog intact (factor 1.8) would need 709 kcal and about 187 g, while a weight-loss target (factor 1.0) drops it to 394 kcal and 104 g. Same animal, same bowl, wildly different correct answers.

Using the Numbers for Weight Management

The calculator gives you a starting baseline, not a verdict. The real instrument is your hands. Feel the ribs: you should feel them easily under a thin layer of fat, not see them poking out and not have to press through padding. Look from above for a visible waist behind the ribs, and from the side for a tucked-up belly. That's a body condition score around the ideal middle.

Feed the calculated amount for four weeks, then reassess. If the waist is disappearing and the ribs are getting harder to find, cut food by 10% and hold. If ribs are sharpening and energy is dropping, add 10%. Adjust in small steps — 10% at a time — and give each change a few weeks to show. For tracking the trend over months, a simple weight loss tracker works just as well for a dieting dog as for a person.

My Own Reset

I ran my own dog through this after his neuter surgery and felt slightly embarrassed. I'd been feeding two level cups of a 360 kcal-per-cup kibble — 720 kcal — to a 9 kg dog whose post-surgery daily target turned out to be about 570 kcal. That's a 26% overshoot, every single day, for the better part of a year. The vet's "he could lose a little" suddenly had a number attached. Dropping to one and a half cups and weighing the difference on a kitchen scale took him from a soft 11 kg back to a firm 9.5 kg over about three months, no drama, just smaller meals that matched the actual math.

If you're also juggling your pet's age or your own calorie targets, the pet age calculator and the calorie calculator cover those side quests.

A Note on Scope

This is informational, not veterinary advice. The RER and MER formulas are population averages from the NRC and WSAVA frameworks, and individual needs drift by ±20% with breed, body condition, coat, season, and underlying conditions — a hypothyroid dog needs roughly 15% less, a hyperthyroid cat roughly 30% more. Puppies, pregnant or nursing animals, and any pet with a diagnosed metabolic, kidney, or thyroid condition should be fed under a veterinarian's direction. Use these numbers as the baseline you walk into the clinic with, and let your vet and your hands on the ribs make the final call.

Made by Toolora · Updated 2026-06-13