How this calculator works
Veterinary nutrition starts from the Resting Energy Requirement (RER) — the energy a dog burns at rest in a neutral environment:
RER = 70 × (body weight in kg)0.75
Daily needs are then estimated by multiplying RER by a life-stage factor. These factors are the ranges used in standard veterinary references:
| Life stage | Factor × RER |
|---|---|
| Puppy under 4 months | 3.0 |
| Puppy 4–12 months | 2.0 |
| Neutered adult | 1.6 |
| Intact adult | 1.8 |
| Senior / less active | 1.2–1.4 |
| Weight loss (ideal weight) | 1.0 |
| Very active / working | 2.0–5.0 |
Two dogs of the same weight can genuinely differ by ±20% or more, so treat the result as a starting ration: feed it consistently for 2–4 weeks, check your dog's body condition (you should feel ribs easily but not see them), and adjust in ~10% steps.
Don't forget that treats count. A good rule of thumb is to keep treats under 10% of daily calories — for a 1,000 kcal/day dog, that's a 100 kcal budget.
Once you have a kcal target, the food portion & cost calculator converts it into grams or cups of your specific food, and tells you how long a bag will last.
Frequently asked questions
How many calories does a 20 kg (44 lb) dog need?
A typical neutered adult at 20 kg has an RER of about 662 kcal, and a daily need of roughly 1,060 kcal (662 × 1.6). An intact, more active dog of the same weight lands closer to 1,190–1,320 kcal.
Why does my food bag recommend a different amount?
Feeding guides on bags are averages across many dogs and often run generous. The RER method is individual to your dog's weight and life stage. If the two disagree, start between them and adjust based on body condition over a few weeks.
My dog is overweight — do I use current or target weight?
Use the ideal weight with the weight-loss factor (× 1.0). Aim for gradual loss — around 1–2% of body weight per week — and involve your vet, especially for large reductions.