How much should you feed a dog?
A dog's daily food is set by how much energy its body needs, not by a one-size-fits-all cup count. Veterinary nutritionists estimate that need in two steps and then convert calories into a portion of the specific food you buy. This calculator follows the same method used in the WSAVA and AAHA nutrition guidelines.
The RER/MER formula
First, the Resting Energy Requirement (RER) — the calories a dog burns at rest — is:
RER (kcal/day) = 70 × (body weight in kg)0.75
The 0.75 exponent (metabolic body weight) is why a 40 kg dog does not need twice the food of a 20 kg dog: energy use rises more slowly than body mass. Next, the Maintenance Energy Requirement (MER) scales RER by a life-stage and activity factor:
MER = RER × factor
Finally, the daily portion is MER ÷ the calorie density of the food (kcal per cup or per gram, printed on the bag as "calorie content" or metabolizable energy).
Standard life-stage factors
- Neutered adult: 1.6 · Intact adult: 1.8
- Weight loss: 1.0 · Weight gain / senior gain: 1.4
- Puppy 0–4 months: 3.0 · Puppy 4 months to adult: 2.0
- Active / working dogs: 2.0–5.0 depending on workload
A worked example
For a 20 kg neutered adult dog: RER = 70 × 200.75 = 70 × 9.457 ≈ 662 kcal/day. MER = 662 × 1.6 ≈ 1,059 kcal/day. If the kibble provides 360 kcal per cup, that is 1,059 ÷ 360 ≈ 2.9 cups per day, best split into two meals of about 1.5 cups.
Why label feeding charts often overfeed
The chart on a food bag assumes an average, moderately active dog and rounds up. Most pet dogs in North America are spayed or neutered and less active than that assumption, so bag charts commonly suggest 20–30% more than a neutered adult actually needs. Feeding to the calculated MER and then adjusting by body condition is more reliable.