PetSums

Dog food calculator

Enter your dog's weight and the kcal per 100g from the food bag to see how many grams to feed each day.

For weight loss, enter the target weight your vet suggested.

On the bag as metabolisable energy. If it says per kg, divide by 10.

Meals a day

Enter her weight and the kcal from the bag to see daily grams.

How much food a dog needs

A 20kg neutered adult dog needs roughly 930 to 1,060 kcal a day. On a dry food with 380 kcal per 100g, that's about 245 to 280g a day. The grams change with every food, which is why the calculator asks for the kcal on your bag rather than giving a one-size chart.

How this is calculated

The calculator follows the method in the AAHA nutrition and weight management guidelines, which vets use as a starting point.

  1. Resting energy requirement (RER) = 70 × body weight in kg0.75.
  2. Daily energy need = RER × a life stage factor from the table below.
  3. Grams a day = daily kcal ÷ kcal per 100g × 100.
Life stage factors used
Life stageFactor × RER
Adult, neutered1.4 to 1.6
Adult, not neutered1.6 to 1.8
Puppy under 4 months3.0
Puppy 4 months or older2.0
Weight loss (use target weight)1.0
Working dog, light work1.6 to 2.0
Working dog, moderate work2.0 to 5.0

AAHA notes that dogs who mostly lie about indoors may need less than these figures, so treat the lower number as your starting point for a sofa dog.

Worked example

Max is a neutered Springer Spaniel weighing 20kg. His dry food has 380 kcal per 100g.

RER = 70 × 200.75 = 662 kcal. Daily need = 662 × 1.4 to 1.6 = 927 to 1,059 kcal. Grams = 927 ÷ 380 × 100 to 1,059 ÷ 380 × 100 = 244 to 279g a day, or 122 to 139g at each of two meals. His treat allowance is about 106 kcal a day.

Checking you've got it right

Weigh your dog every two to four weeks. If she's gaining weight she shouldn't, move towards the lower figure or below it; if she's losing weight, move up. Puppies need re-calculating as they grow, so redo the sums every couple of weeks using their current weight, and switch to the 4 months and older factor at that age.

This calculator doesn't cover pregnant or nursing bitches, dogs with medical conditions, or homemade raw diets. Ask your vet for those.

Questions people ask

How much should I feed my dog a day?

It depends on her weight, life stage and the energy in the food, so the same dog might need 250g of one dry food and 300g of another. Find the kcal per 100g on the bag, enter it with her weight, and the calculator gives a daily range in grams. Then weigh her every few weeks and adjust.

Where do I find the kcal on dog food?

Look on the bag or tin near the analytical constituents or feeding guide. It's usually written as metabolisable energy (ME), either per 100g or per kg. If it's per kg, divide by 10 to get the figure per 100g.

Why is the calculator different from the feeding guide on the bag?

Bag guides are written for a typical dog and often cover a wide weight band. This calculator works from your dog's exact weight and whether she is neutered, which changes her energy needs. Both are starting points: her body shape over the next few weeks tells you which one is closer.

How much of my dog's food can be treats?

PDSA advises that treats shouldn't take up more than 10% of your dog's daily food allowance, and that you cut her usual food by the same amount. The calculator shows that 10% in kcal.

How do I feed a dog that needs to lose weight?

Use her target weight rather than her current weight and choose the weight loss option. AAHA guidance uses resting energy needs with no extra allowance for weight loss. Ask your vet to set the target weight and check her progress.

Sources

  1. AAHA 2021 Nutrition and Weight Management Guidelines: weight reduction in the obese pet
  2. PDSA: How to treat your dog

Figures checked on 25 October 2026. Read how we calculate for the rounding and assumptions behind every tool.