Pet Food Calculator
Feeding by Weight, Not by the Bag's Suggestion
The feeding chart printed on a bag of dog or cat food is a rough average for the entire breed and life stage — it rarely accounts for whether an animal is neutered, working, recovering from illness, or still growing. Veterinary nutritionists instead size a daily ration from the animal's actual metabolic energy need, then convert that need into cups of a specific food using its calorie density. This calculator runs that two-step math directly, so the result is tied to your pet's real weight and the food you're actually feeding, not a generic label.
The Formula
MER (kcal/day) = RER × Life-Stage / Activity Factor
Cups/day = MER ÷ Calories per Cup of Food
RER is the Resting Energy Requirement — the calories an animal burns at rest, doing nothing but existing. MER, the Maintenance Energy Requirement, scales that baseline up or down according to how active, intact, or young the animal is, since a working dog and a dog recovering from surgery have very different real-world needs from the same body weight.
Why the Multiplier Matters So Much
- Weight management — using the "inactive / weight loss" factor instead of "neutered adult" can cut the daily ration by close to 40%, which is the difference between a diet plan working and stalling.
- Growth stages — puppies and kittens carry a factor around 2.5, reflecting the extra energy growth itself consumes, well above any adult multiplier.
- Switching foods — because the formula divides by calories per cup, swapping to a denser or lighter kibble automatically changes the recommended cup count without changing the underlying energy target.
| Species | Life stage / activity | Factor | MER (kcal/day) | Cups/day |
|---|---|---|---|---|
| Dog (20 kg) | Inactive / weight loss | 1.0 | 662 | 1.89 |
| Dog (20 kg) | Neutered adult | 1.6 | 1059 | 3.03 |
| Dog (20 kg) | Intact adult | 1.8 | 1192 | 3.4 |
| Dog (20 kg) | Puppy | 2.5 | 1655 | 4.73 |
| Dog (20 kg) | Active / working | 3.0 | 1986 | 5.67 |
| Cat (4 kg) | Inactive / weight loss | 1.0 | 198 | 0.66 |
| Cat (4 kg) | Neutered adult | 1.2 | 238 | 0.79 |
| Cat (4 kg) | Intact adult | 1.4 | 277 | 0.92 |
| Cat (4 kg) | Active / working | 1.6 | 317 | 1.06 |
| Cat (4 kg) | Puppy / kitten | 2.5 | 495 | 1.65 |
RER computed as 70 × (weight in kg)0.75; cups/day rounded to two decimals.
How to Use This Calculator
- Choose the species: Dog or Cat.
- Enter the pet's weight in kilograms.
- Select the life stage / activity level that best matches your pet (neutered adult, intact adult, inactive/weight loss, active/working, or puppy/kitten).
- Optionally enter the calories per cup for the specific food you feed — it defaults to 350 kcal/cup if left blank.
- Select Calculate to see the daily kcal target and the equivalent cups of food per day.
Related Calculations
For weight-specific dog or cat feeding without a manual kg-to-lb conversion, see the Dog Food Calculator and Cat Food Calculator.