Why doesn't the result match the feeding guide on the bag?

Both are starting points. Bag guides are written by the manufacturer for an average dog of each weight; this calculator uses the veterinary RER formula and life-stage factors. Either can be off for your dog. Weigh your dog every few weeks and adjust with your vet.

Where do I find kcal per cup?

Look for "calorie content" on the bag, usually written as kcal/kg and kcal/cup. If it only gives kcal/kg, the manufacturer can tell you the kcal per cup, or you can weigh the food in grams instead of using cups.

Should I use my dog's current weight or ideal weight?

For a dog at a healthy weight, the current weight. For weight loss, veterinary references base calories on the ideal (target) weight. Our ideal weight calculator gives a rough target, but agree on it with your vet.

What about pregnant or nursing dogs?

Their needs rise a lot, especially while nursing, and change week by week. We don't include them because a fixed factor would mislead. Ask your veterinarian for a feeding plan.

How accurate is this?

AAHA's nutrition guidelines say the energy needs of individual dogs can vary by 30% in either direction from calculated values. That's why the calculator also shows a variation range, and why body condition, not the formula, should guide changes.

Dog Food Calculator: Daily Calories and Cups per Day

By Marcos Ortega · Updated October 25, 2026 · Runs in your browser; nothing you type is sent anywhere.

Educational estimate, not veterinary advice. These numbers come from published averages and can be wrong for your pet. Your veterinarian, who can examine your dog or cat, is the right person to decide what is healthy for them.

How much to feed a dog comes down to two numbers: how many calories the dog needs per day, and how many calories are in one cup of its food. This calculator estimates the first with the standard veterinary formula and divides by the second, which you read from your bag.

Step 1: resting energy requirement (RER)

The RER is the energy a dog uses at rest in a comfortable environment. The Merck Veterinary Manual gives it as:

RER (kcal/day) = 70 × (body weight in kg)^0.75

Raising weight to the power 0.75 reflects the fact that a dog twice as heavy doesn’t need twice the energy. To convert pounds to kilograms, divide by 2.2046. Merck also gives a simpler linear version, 30 × kg + 70, for dogs between 2 and 45 kg; the calculator always uses the exponent formula, which works at every weight.

Step 2: multiply by a life-stage factor

The maintenance energy requirement (MER) is the RER times a factor for the dog’s life stage and activity. These are the factors from Ohio State University’s veterinary Nutrition Support Service (the Merck Veterinary Manual gives the same values for the rows they share):

Dog	Factor (× RER)
Adult, spayed/neutered	1.6
Adult, intact	1.8
Inactive or obesity-prone	1.2–1.4 (calculator uses 1.4)
Weight loss	1.0 × RER for ideal weight
Active or working	2.0–5.0 (calculator uses 2.0)
Puppy, 0–4 months	3.0
Puppy, 4 months to adult	2.0

For ranges, the calculator starts at the value shown and lists the range so you can see how wide it is. Working dogs especially vary: a sled dog in winter and a farm dog on a quiet day are not the same.

Step 3: subtract treats, then convert to cups

The World Small Animal Veterinary Association (WSAVA) advises that treats should make up less than 10% of a dog’s daily calories. The calculator sets aside the treat percentage you enter (10% by default) and divides the rest by your food’s calories per cup.

Daily calories by weight

Weight	RER	Neutered adult (1.6)	Intact adult (1.8)	Puppy 4 mo+ (2.0)	Puppy 0–4 mo (3.0)
5 lb	129	207	233	259	388
10 lb	218	348	392	435	653
20 lb	366	585	659	732	1,098
40 lb	615	985	1,108	1,231	1,846
60 lb	834	1,335	1,501	1,668	2,502
80 lb	1,035	1,656	1,863	2,070	3,105
100 lb	1,223	1,958	2,202	2,447	3,670

kcal per day, rounded. Puppy rows use the puppy’s current weight.

Worked examples

Example 1: a 40 lb neutered adult dog, food with 380 kcal per cup, 10% treats. 40 lb ÷ 2.2046 = 18.14 kg. 18.14^0.75 = 8.79. RER = 70 × 8.79 = 615 kcal. MER = 615 × 1.6 = 985 kcal per day. Treats: 10% = 98 kcal. Food: 985 − 98 = 886 kcal ÷ 380 = 2.33 cups per day. Normal variation (±30%): 689–1,280 kcal.

Example 2: weight loss for a 60 lb dog whose vet sets a 50 lb target. Use the target: 50 lb = 22.68 kg, RER = 727 kcal, × 1.0 = 727 kcal per day. For comparison, maintaining 60 lb as a neutered adult would be 1,335 kcal. That’s why weight-loss diets are planned with a vet, who also checks progress.

Example 3: a 22 lb (10 kg) puppy, 3 months old. RER = 70 × 10^0.75 = 70 × 5.62 = 394 kcal. × 3.0 = 1,181 kcal per day. Puppy needs change quickly as they grow, so recalculate every couple of weeks.

Limitations

Individual variation is large. AAHA’s nutrition guidelines note that energy needs can differ by 30% in either direction from calculated values in dogs. Ohio State’s calorie calculator page warns that needs can differ by about 50% from calculated values.
The body is the real gauge. If your dog gains or loses weight on the calculated amount, adjust. Our ideal weight calculator explains body condition scoring.
Not for every dog. Pregnant and nursing dogs, dogs with medical conditions and dogs on prescription diets need a plan from a veterinarian.
Cups are imprecise. A “cup” scooped by hand can vary a lot. A kitchen scale and the kcal/kg on the bag are more accurate.

Dog Food Calculator: Daily Calories and Cups per Day