How this dog food calculator works
Vets estimate a dog's calorie needs in two steps. First they calculate the resting energy requirement (RER), the calories a dog burns lying still in a comfortable room. Then they multiply it by a life stage factor to get the daily energy requirement, sometimes called maintenance energy requirement (MER). This is the approach used in the WSAVA Global Nutrition Committee toolkit and the AAHA nutrition guidelines.
Once you know calories, the cups are just division: calories per day divided by the kcal per cup printed on your food. That's why this calculator asks for the label value instead of assuming a "standard" cup. Dry foods range from about 300 to over 450 kcal per cup, so the same dog can need 1.8 cups of one food and 2.6 cups of another.
The formula
RER = 70 × (weight in kg)0.75
daily calories = RER × life stage factor
cups per day = daily calories ÷ kcal per cup
days per bag = (bag lb × 0.4536 × kcal per kg) ÷ daily calories
Life stage factors used
| Dog | Factor × RER |
|---|---|
| Puppy under 4 months | 3.0 |
| Puppy 4 months to adult size | 2.0 |
| Neutered or spayed adult | 1.6 |
| Intact adult | 1.8 |
| Less active, senior or weight-gain prone | 1.4 |
| Weight loss (at goal weight) | 1.0 |
| Active or light work | 2.0 |
| Moderate work | 3.0 |
These are the commonly published textbook factors. Heavy working dogs such as sled dogs can need 4 to 8 times RER, which is beyond what a general calculator should guess at.
Example: a 30 lb neutered adult
A 30 lb (13.6 kg) spayed dog eating a kibble with 350 kcal per cup and 3,600 kcal per kg, fed twice a day from a $60, 30 lb bag:
| Step | Result |
|---|---|
| RER = 70 × 13.610.75 | 496 kcal |
| Daily calories = 496 × 1.6 | 794 kcal |
| Cups per day = 794 ÷ 350 | 2.27 cups |
| Cups per meal (2 meals) | 1.13 cups |
| Bag calories = 30 × 0.4536 × 3,600 | 48,988 kcal |
| One bag lasts | 62 days |
| Bags per month / cost per month | 0.49 bags / $29.55 |
In practice, 2.27 cups is "a generous 2¼ cups a day," or a bit over 1 cup per meal.
Tips for getting portions right
- Use a real measuring cup, or better, a scale. A "cup" scooped with a coffee mug can be 30% more than a standard 8 oz cup. Weighing grams is the most accurate method.
- Judge by body condition, not the number. You should be able to feel the ribs easily under a thin layer of fat and see a waist from above. If not, cut portions by 10% and recheck in 2–4 weeks.
- Individual dogs vary a lot. Two dogs of the same weight can differ in needs by 20–30% or more. Treat the result as a starting point.
- Count treats and chews. Keep them to about 10% of daily calories and trim meals to match.
- Puppies change fast. Recalculate every couple of weeks as they grow, and use their current weight.
This calculator is an educational estimate, not veterinary advice. Check your food's label and ask your vet, especially for puppies, pregnant or nursing dogs, seniors, or dogs with a medical condition.
Frequently asked questions
How many cups of food should my dog eat a day?
It depends on weight, life stage and how calorie-dense the food is. A 30 lb neutered adult needs roughly 790 calories a day, which is about 2.25 cups of a 350 kcal/cup kibble. A richer food means fewer cups, so always convert from calories rather than copying someone else's cup count.
Where do I find kcal per cup on dog food?
In the US, the calorie statement is printed on the bag or can, usually near the guaranteed analysis, as kcal/kg and kcal per cup or per can. Most dry foods fall between about 325 and 450 kcal per cup. If it is not on the label, check the brand's website.
Is the feeding chart on the bag accurate?
Bag charts are a reasonable starting range, but they are written to cover active, intact dogs and often overshoot for neutered or indoor dogs. Use the label or this calculator as a starting point, then adjust by 10% up or down based on your dog's body condition over a few weeks.
How much should I feed my dog to lose weight?
A common veterinary starting point is 1.0 times the resting energy requirement calculated at the dog's target weight, not its current weight. Enter the goal weight and choose the weight loss option, and work with your vet so the loss stays around 1-2% of body weight per week.
How many times a day should I feed my dog?
Most adult dogs do well on two meals a day. Young puppies usually eat three or four smaller meals. Splitting the daily amount does not change the total calories, only the portion size.
Do treats count toward daily calories?
Yes. Keep treats to about 10% of daily calories and reduce meals to match. For a dog that needs 800 kcal, that is roughly 80 kcal of treats per day.
Rates and figures last checked September 2026.
This calculator gives estimates for planning. Check current rates and product labels before you buy, list or file.