If you've ever turned over your dog's food bag and tried to follow the feeding chart, you've hit the same wall every dog owner does: the recommended portion seems too much, or not enough, and there's no way to tell which.
That's because the chart isn't wrong — it's generic. It targets the "average" intact, active adult dog of a given weight. Most pet dogs aren't that. They're neutered, less active, and live indoors. Feed the bag amount to most house dogs and weight creeps up year after year.
Veterinary nutritionists don't use the bag. They use a two-step formula that's been the standard for decades — and once you understand it, you'll never look at portion guidance the same way again.
Step 1 — Resting Energy Requirement (RER)
RER is what your dog burns at complete rest. Heart beating, lungs breathing, brain running, organs metabolising — but no movement, no digestion of a recent meal, no temperature regulation effort. It's the minimum calorie cost of being alive.
RER = 70 × (body weight in kilograms)0.75
The strange-looking exponent (0.75) isn't arbitrary. Smaller animals burn more calories per kilogram than larger ones because their surface area is large relative to their mass — they lose more heat. The 0.75 power scales the formula correctly across the enormous size range of dogs, from 2 kg Chihuahuas to 80 kg Mastiffs.
You don't need to calculate this by hand. A 10 kg dog has an RER of about 393 kcal; a 25 kg dog about 783 kcal; a 40 kg dog about 1,113 kcal. Our calorie calculator does this instantly.
Step 2 — Maintenance Energy Requirement (MER)
RER alone doesn't cut it because real dogs aren't lying still all day. They walk, run, play, regulate body temperature outdoors, digest food. MER is RER multiplied by a factor that captures all of this.
Typical multipliers
- Neutered adult dog — 1.6 × RER
- Intact adult dog — 1.8 × RER
- Puppy under 4 months — 3.0 × RER
- Puppy 4–12 months — 2.0 × RER
- Sedentary house dog — 1.0–1.4 × RER
- Working / sporting dog — 2.0–5.0 × RER
Notice something? Neutering drops calorie needs by about 11–25%. This is one of the most under-appreciated facts in dog ownership. A dog that needed 800 kcal as a young, intact adult might genuinely only need 600 kcal after neutering — yet most owners don't change the portion.
The dog isn't suddenly greedy. Their metabolism has changed, and the food bowl hasn't.
Putting it together — a real example
Say you have a 15 kg, neutered, moderately active Border Collie.
- RER = 70 × (15)0.75 ≈ 533 kcal
- MER = 533 × 1.6 = 853 kcal/day
If your kibble shows 380 kcal per cup, that's 2¼ cups per day, split into two meals. The food bag might recommend 3 cups — leading to a 30% calorie surplus that adds up to several pounds of weight gain over a year.
The treats trap
Treats and "just a bit" of human food are how most carefully calculated diets quietly fail. A standard dental chew can be 80–100 kcal. A small piece of cheese, 50 kcal. A few biscuits a day quickly add up to 200 kcal — which for a 10 kg dog is 50% of their entire RER.
The rule veterinary nutritionists use: treats should not exceed 10% of daily calorie target. For our Border Collie above, that's about 85 kcal of treats per day — total.
When to recalculate
- After neutering — re-run the numbers with the lower multiplier.
- After significant lifestyle changes — new job means less exercise? Recalculate.
- When entering the senior years (7+ for medium dogs, earlier for large breeds).
- Any time your dog's body condition drifts from BCS 4–5.
The honest caveat
Even this formula is a starting point, not a prescription. Individual dogs vary by 20–30% in metabolic efficiency. The real test is your dog's body condition over time. Calculate the target, feed it for 2–3 weeks, then re-assess BCS. Adjust by ±10% and repeat.
This is exactly what veterinarians do. The math gets you in the right neighbourhood; observation finds the right house.