How much should I feed my dog or cat?
There is a real formula behind this, it is not complicated, and it is worth understanding rather than guessing from the side of the bag. Here it is in full — plus the three places it goes wrong, and when the answer is to call your vet instead.
The formula
Veterinary nutrition works in two steps. First, resting energy requirement — what an animal burns doing nothing:
RER = 70 × (bodyweight in kg)0.75
The ¾ power matters: energy needs do not scale linearly with size. A 60 lb dog does not need twice the calories of a 30 lb dog — it needs about 68% more. This is why "a cup per 20 lb" style rules of thumb overfeed large dogs and underfeed small ones.
Second, multiply RER by a factor for life stage, neuter status and activity to get maintenance energy requirement (MER), the actual daily target.
The life-stage factors we use
| Life stage | Dog | Cat | Why |
|---|---|---|---|
| Puppy / kitten, 0–4 months | ×3 | ×2.5 | Growth is the most calorie-hungry state there is. |
| Puppy / kitten, 4–12 months | ×2 | ×2 | Growth slowing, but still well above adult needs. |
| Adult, intact | ×1.8 | ×1.4 | Baseline adult maintenance. |
| Adult, neutered | ×1.6 | ×1.2 | Neutering lowers requirement by roughly 11% — a very common cause of post-neuter weight gain. |
| Senior | ×1.4 | ×1.1 | Lower activity and lean mass. |
Activity then adjusts an adult's figure between ×0.9 and ×1.15 for dogs. It does not adjust a growing or senior animal, whose factor already reflects its state.
Where this goes wrong
Feeding to the current weight instead of the target weight
If a pet is overweight, running the formula on today's weight simply maintains the problem. Feed for the ideal weight. A body condition score helps: on the 9-point scale, 5 is ideal and every point above it is roughly 10% more bodyweight than it should be. A 60 lb dog at 7/9 is carrying about 20% excess, so the target is nearer 50 lb — and the daily ration should be calculated from 50, not 60.
Treating treats as extra
Treats belong inside the daily total. We carve out 10% for them, so the meal portion is 90% of MER. A few training treats and a dental chew can quietly be a fifth of a small dog's daily calories.
Guessing the food's calorie density
Foods range roughly from 300 to 500 kcal per cup, so the same portion can be a third more food than intended. Find "kcal ME/cup" on the bag and use it. Better still, weigh the food: cups vary with how you scoop, grams do not.
A worked example
A neutered adult dog at an ideal 60 lb, moderate activity, on a food at 380 kcal/cup:
- 60 lb ÷ 2.2046 = 27.2 kg
- RER = 70 × 27.20.75 = 834 kcal
- MER = 834 × 1.6 (neutered adult) × 1 (moderate) = 1335 kcal/day
- Food = 90% of that = 1201 kcal ÷ 380 = 3.2 cups/day, split across meals
- Treat allowance = 133 kcal/day
When to call your vet instead
A calculator is a starting point for a healthy animal. Some situations need a professional, not arithmetic:
- Any weight-loss plan, particularly for cats — rapid loss risks hepatic lipidosis, which is life-threatening.
- Unexplained weight change on unchanged food. Thyroid disease, diabetes, kidney disease and cancer all present this way.
- Pregnancy or nursing, where requirements rise dramatically and change week to week.
- Any diagnosed condition — kidney, cardiac, hepatic, diabetic and orthopaedic cases are managed with prescription diets whose targets are not these ones.
- Growing large-breed puppies, where overfeeding and excess calcium are linked to developmental orthopaedic disease. Growth rate matters as much as total calories here.
- A pet that will not eat for more than a day or two, which is an urgent sign in cats especially.
Nothing on this page is veterinary advice, and no licensed veterinarian reviewed it. It is the standard energy model, shown transparently so you can check it — your vet knows your animal.