Key takeaways
- Daily calories come from RER × an activity factor (MER).
- RER = 70 × (body weight in kg)0.75 — the resting baseline.
- A 40 lb neutered adult needs about 984 kcal/day.
- Keep treats ≤ 10% of daily calories (≈ 98 kcal here).
How a dog's daily calories are calculated
Vets size a dog's diet in two steps. First the resting energy requirement (RER) — the calories burned at complete rest — is found from metabolic body weight. Then RER is multiplied by an activity factor for life stage and exercise to get the maintenance energy requirement (MER), the number you actually feed to. Treats are then capped at about 10% of that total so the complete diet stays balanced.
This is why two dogs of the same weight can need very different amounts: an active working dog burns far more than a senior or a dog on a weight-loss plan.
Worked example: a 40 lb neutered adult
40 ÷ 2.2046 = 18.14 kg. RER = 70 × 18.140.75 ≈ 615 kcal. MER = 615 × 1.6 ≈ 984 kcal/day. Treat budget = 10% of 984 ≈ 98 kcal from treats, with the rest from complete food.
MER activity factors
| Life stage / activity | Factor | Notes |
|---|---|---|
| Weight loss | 1.0 | Applied to target weight; feed at resting level. |
| Senior / inactive | 1.2 | Older or low-activity adult dogs. |
| Neutered adult | 1.6 | Typical spayed/neutered pet at a healthy weight. |
| Intact adult | 1.8 | Un-neutered adult with normal activity. |
| Active / working | 2.5 | High exercise; working and sporting dogs. |
| Puppy (under 4 mo) | 3.0 | Fast growth; feed a complete puppy diet. |
What to do with the number
Use the daily total to portion food: divide MER by the calories per cup printed on your food's label to get cups per day, then split across meals. To turn calories into a feeding amount, try the dog food calculator, and to raise activity (and the factor) plan with the dog walk & exercise calculator.
Frequently asked questions
How many calories does my dog need per day?
It depends on weight and activity: RER (70 × kg^0.75) × an activity factor. A 40 lb neutered adult needs about 984 kcal/day.
What is the difference between RER and MER?
RER is calories burned at rest; MER is RER × an activity factor for life stage and exercise — the number you feed to.
How does the 10% treat rule work?
Treats should be ≤ 10% of daily calories so the main diet stays balanced — about 98 kcal for a dog needing 984 kcal/day.
How do activity and neuter status change it?
Neutered adults use ~1.6, intact ~1.8, active/working 2.0–5.0, and weight-loss ~1.0 on ideal weight.
What about a dog that needs to lose weight?
Use a factor of about 1.0 on the target weight, not current weight — and plan it with your vet.
How many calories does a puppy need?
Much more — about 3.0× for pups under 4 months, ~2.0× from 4 months to adult. Feed a complete puppy diet.
Energy formulas (RER = 70 × kg^0.75 and life-stage MER factors) follow established veterinary nutrition standards — see WSAVA / AAFCO guidance. Reviewed by a veterinarian.
Last reviewed June 2026