How Many Calories Does a Dog Need a Day? The Full Formula Explained
"How much should I feed my dog" doesn't have a single answer, because it depends on weight, age, activity and whether they're desexed. But it isn't a guessing game either. Vets and veterinary nutritionists use a specific formula, and you can use the exact same one at home.
Step 1: resting energy requirement (RER)
Resting energy requirement is the energy a dog burns just existing, lying down, doing nothing. It's the foundation every other calculation builds on. The standard veterinary formula is:
RER = 70 × (weight in kg)0.75
The exponent looks odd, but it exists because energy needs don't scale in a straight line with weight, a 40 kg dog doesn't need exactly twice the calories of a 20 kg dog, it needs a bit less than double, because larger animals are metabolically more efficient per kilogram. This formula, from the AAHA's nutrition and weight management guidelines, is the same one vets enter into their own software.
Step 2: multiply for activity (MER)
RER assumes a dog is doing nothing. Maintenance energy requirement (MER) scales it up for however active they actually are:
| Activity level | Multiplier (desexed) | Multiplier (entire) |
|---|---|---|
| Mostly rests, short potty walks | 1.2–1.4 | — |
| Short daily walks (20–30 min) | 1.4–1.6 | — |
| Active most days (45–60 min, play) | 1.6–1.8 | — |
| Very active (runs, hikes, sport) | 1.8–2.0 | — |
Dogs that haven't been desexed typically need a little more again, roughly the top of these ranges or slightly above, because entire animals tend to run a higher baseline metabolism.
Worked examples
A 5 kg desexed dog, short daily walks: RER = 70 × 50.75 ≈ 234 kcal. MER = 234 × 1.5 ≈ 350 kcal a day.
A 20 kg desexed dog, active most days: RER = 70 × 200.75 ≈ 661 kcal. MER = 661 × 1.7 ≈ 1,124 kcal a day.
A 35 kg entire dog, active most days: RER = 70 × 350.75 ≈ 1,036 kcal. MER = 1,036 × 1.8 ≈ 1,865 kcal a day.
Adjustments worth knowing
- Seniors typically need about 10% less than an adult of the same weight and activity level, metabolism slows with age.
- Puppies don't follow MER at all, they need roughly twice their resting energy as a growth allowance, and that changes every few weeks as they grow. Giant breed puppies need a vet-guided controlled growth diet, not a generic multiplier.
- Weight loss targets feed the resting energy of the dog's healthy weight, not their current weight, which is the standard starting point vets use, then adjusts from there based on how the dog actually responds.
Why this is a starting point, not a fixed number
Published equations for calorie needs can be off by as much as 50% for an individual dog. Metabolism varies by breed, by the individual, by how a food's actual calorie content compares to its label. That's exactly why every vet-recommended approach treats the formula as a starting point: feed the calculated amount, weigh the dog every couple of weeks, and adjust up or down by about 5–10% based on what actually happens on the scale.
Don't want to do the maths by hand? The free dog calorie calculator runs these exact formulas for you, or get a full portion-by-weight plan with the free 60-second check.
Get your own dog's healthy weight range, a calorie target, and a 7-day plan built for their breed, age and activity. Free to start.
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