Dog Food Calculator
Enter your dog's weight and activity level to estimate daily calorie needs and cups of food per day.
Last updated: September 25, 2026
Frequently asked questions
How much food does a 40 lb dog need per day?
A moderately active 40 lb dog needs roughly 985 calories per day, or about 2.8 cups of a food with 350 calories per cup.
What is RER for dog food calculations?
Resting energy requirement (RER) is the calories a dog needs at complete rest, calculated as 70 × (weight in kg)^0.75 - daily needs are then scaled up from RER based on activity level.
Should I adjust the amount for a spayed or neutered dog?
Yes, generally - spayed and neutered dogs often have a slightly lower metabolic rate, so many veterinarians recommend reducing the calculated portion by roughly 10-20% to avoid gradual weight gain, then adjusting further based on your dog's actual body condition over time.
How does dog food calorie density affect how much to feed?
Not all dog foods have the same calorie density - a cup of a calorie-dense food delivers more energy than a cup of a lower-calorie formula, so the same daily calorie target translates into different serving sizes depending on the specific food's calories-per-cup, listed on the packaging.
How much food does a working or very active dog need compared to a moderate one?
An active/working dog typically needs a higher activity multiplier applied to RER, often 20-40% more calories than a moderately active dog of the same weight - a 40 lb working dog can need well over 3 cups a day versus roughly 2.8 cups at moderate activity.
Why does the calculator ask for a puppy activity level instead of just using weight?
Growing puppies need substantially more calories per pound than adult dogs to support tissue development, so selecting 'puppy' applies a higher multiplier to the RER-based estimate rather than treating them like a sedentary adult of the same weight.
Is 'cups per day' the same across every brand of dog food?
No - this calculator converts your calorie target into cups using the calories-per-cup value you enter, which varies by brand and formula. Always check your specific food's label for its calorie density rather than assuming a universal cup size.