How much to feed your dog: the calorie math, step by step

To work out how much to feed, first calculate your dog’s resting energy requirement (RER = 70 × body weight in kg to the power of 0.75). Multiply it by a factor for life stage and activity to get daily calories. Then divide by the kcal per cup on your bag. For a typical neutered 20 kg adult, that’s about 1,060 kcal a day, or just under 3 cups of a 372 kcal/cup kibble.

Treat the result as a starting point. Weigh your dog every two to four weeks and adjust.

Step 1: find your dog’s weight in kilograms

Use your dog’s current weight if they’re at a healthy body condition. If your dog is overweight, use the target weight your vet gives you, not the current weight.

To convert pounds to kilograms, divide by 2.2. A 44 lb dog weighs 20 kg.

Step 2: calculate the resting energy requirement (RER)

RER is the energy a dog uses at rest in a comfortable environment. The formula vets most often use is:

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

The “^0.75” means “to the power of 0.75”. On a phone calculator, type the weight, press x^y, type 0.75, then multiply by 70.

Some RER values:

Weight	RER
5 kg	234 kcal
10 kg	394 kcal
20 kg	662 kcal
30 kg	897 kcal
40 kg	1,113 kcal

Bigger dogs need more energy in total, but less per kilogram. That’s why the formula uses a power of 0.75 rather than simple multiplication.

Step 3: multiply by a life-stage factor

Your dog’s daily energy need, called the maintenance energy requirement (MER), is RER multiplied by a factor. These are the starting factors widely used in veterinary practice:

Dog	Factor (× RER)
Neutered adult, normal activity	1.6
Intact adult, normal activity	1.8
Inactive or prone to weight gain	1.2 to 1.4
Weight loss (applied to target weight)	1.0
Puppy, up to 4 months	3.0
Puppy, 4 months to adult size	2.0
Working or very active dog	2.0 to 5.0

The ranges are wide for a reason. The National Research Council’s reference work on dog nutrition shows large differences in energy needs between individual dogs of the same weight, depending on breed, temperament, coat, housing and activity. Two dogs that look the same on paper can differ by 20% or more in practice.

Step 4: turn calories into cups and grams

Find the calorie statement on your bag. US labels give it in kcal per kilogram and per cup (or per can).

Cups per day = daily kcal ÷ kcal per cup Grams per day = daily kcal ÷ kcal per kg × 1,000

Then split the total into meals. Most adult dogs eat two meals a day; young puppies usually eat three or four.

Worked example: a 20 kg neutered adult

1. Weight: 20 kg
2. RER: 70 × 20^0.75 = 70 × 9.46 = 662 kcal
3. MER: 662 × 1.6 = 1,059 kcal a day
4. The food has 372 kcal per cup and 3,650 kcal per kg:
   • Cups: 1,059 ÷ 372 = 2.85 cups a day, or about 1⅜ cups per meal over two meals
   • Grams: 1,059 ÷ 3,650 × 1,000 = 290 g a day

The same dog on a richer food at 450 kcal per cup needs 2.35 cups. Switching foods without recalculating is one of the easiest ways for a dog to gain or lose weight without anyone noticing.

Puppies need a different approach

Puppies need more energy per kilogram than adults because they’re growing, but their needs change every few weeks. Calculate from the puppy’s current weight, use the puppy factor, and recalculate every two weeks or so as they grow.

Feed a food whose AAFCO statement covers growth. For puppies of breeds expected to weigh 70 lb (about 32 kg) or more as adults, choose a food whose statement specifically includes the growth of large size dogs. Overfeeding large-breed puppies to make them grow faster is a real risk to their joints, so this is a case where your vet’s guidance on target growth matters more than any formula.

Older dogs often need less

Many dogs become less active as they age and lose some muscle, which lowers their energy needs. Others, especially very old dogs, start to lose weight and need more. There’s no single senior factor that fits everyone. Start from the adult factor that matches your dog’s activity, then let the scale and body condition guide you.

Count the treats

Treats, chews and table scraps all have calories. A common rule of thumb in veterinary practice is to keep treats to about 10% of daily calories and cut the main meal by the same amount. For the dog above, that’s roughly 100 kcal of treats a day.

Check, then adjust

The formula gives an estimate. Your dog’s body tells you whether it’s right.

• Weigh your dog every two to four weeks, on the same scale, at the same time of day.
• Check body condition: you should be able to feel the ribs easily under a thin layer of fat, and see a waist from above.
• Adjust by about 10% if weight drifts up or down, then check again in a few weeks.

The WSAVA’s nutrition guidelines recommend a nutritional assessment as part of every vet visit, including body condition and muscle condition scores. Ask your vet to show you how to score your own dog.

When to ask your vet first

Talk to your vet before using any formula for weight loss, for large-breed puppies (whose growth rate needs careful control), for pregnant or nursing dogs, and for dogs with a medical condition. These are the cases where a small error matters most.

Let the calculator do it

Our Feeding Calculator runs these steps for you and uses the exact calorie content of the food you pick from our database. It shows cups and grams per day, split into meals, and compares the result with the bag’s own chart. If your food isn’t listed, you can enter the kcal per cup from the label.

To compare the calorie content of different foods first, read why kcal per cup matters more than the price per bag, or use the Food Finder.