How to Work Out How Many Calories Your Dog Needs

Feeding guides on packaging are averages, produced for a population, and they routinely overestimate what an ordinary pet dog needs. Individual requirements vary by up to about 30 percent either side of any calculated figure.

Here is how to get closer.

The calculation vets use

Step 1: Resting Energy Requirement (RER).

RER = 70 × (body weight in kg)^0.75

For a 20kg dog: 20^0.75 ≈ 9.46, so RER ≈ 662 kcal/day.

If you cannot raise numbers to the power of 0.75 conveniently, a reasonable approximation for dogs between 2kg and 45kg is:

RER ≈ (30 × weight in kg) + 70

For a 20kg dog that gives 670 kcal — close enough for practical purposes.

Step 2: apply a multiplier.

• Neutered adult, typical pet activity: 1.6
• Entire adult: 1.8
• Weight loss: 1.0
• Weight gain: 1.2 to 1.8
• Light work: 2.0
• Moderate work: 3.0
• Heavy work or sled dogs: 4.0 to 8.0
• Puppy under 4 months: 3.0
• Puppy 4 months to adult: 2.0
• Senior, less active: 1.2 to 1.4

For our 20kg neutered pet dog: 662 × 1.6 ≈ 1,060 kcal per day.

Step 3: for weight loss, calculate on target weight, not current weight. A 25kg dog who should be 20kg is fed for a 20kg dog, at the weight-loss multiplier.

Converting calories into food

Every complete food prints a kcal figure — usually per kilogram, per 100g, or per cup. Find it. It is often in small print on the back.

Example: a food with 3,800 kcal/kg. Our dog needs 1,060 kcal.

1,060 ÷ 3,800 = 0.279kg = 279g per day, split into two meals.

Weigh the food

This matters more than the calculation.

Studies of owners measuring dry food with scoops and cups have found errors ranging from substantial underfeeding to overfeeding by 80 percent. The same person using the same cup produces different amounts on different days, and kibble size and shape change how much fits.

A £10 kitchen scale removes the entire problem. Weigh the day’s food in the morning into a container, and use it through the day.

Count the treats

This is where most plans fail quietly.

Treats, chews, training rewards and table scraps should stay under ten percent of daily calories. For our 20kg dog that is 106 kcal — which is:

• About one dental chew, or

• Roughly 25g of cheese, or

• Two small biscuits, or

• Half a pig’s ear

People routinely feed several times that without registering it, and then wonder why a carefully measured bowl has not produced weight loss.

The fix most trainers use: measure the day’s food in the morning and use part of it as training rewards. Kibble works for easy exercises; save the high-value food for hard ones and subtract it.

Then check the dog, not the spreadsheet

The calculation is a starting point. Body condition is the answer.

Every two weeks:

• Ribs: easily felt under a thin layer, like the back of your hand

• Waist from above: a clear inward curve behind the ribs

• Tuck from the side: the belly slopes up towards the hind legs

If your dog is gaining, reduce by ten percent and reassess in two weeks. If losing unintentionally, increase by ten percent. Make one change at a time and give it a fortnight.

Photograph your dog from above and from the side monthly. Change is much easier to see in photographs than in the dog in front of you.

Things that shift requirements

• Neutering. Expect a ten to twenty percent drop

• Age. Requirements usually fall from middle age, then sometimes rise again in very old dogs with poor absorption

• Season. Dogs walked less in winter need less; outdoor dogs in cold climates need more

• Coat. Thick-coated dogs kept outdoors in cold weather burn more

• Illness and recovery. Often increases requirements substantially

• Pregnancy and lactation. Dramatically increases them — lactation can require three to four times maintenance

A rate of loss that is safe

One to two percent of body weight per week. Faster costs lean muscle.

For a 25kg dog aiming for 20kg, that is roughly three to five months. Plan for that.

Making less food feel like more

A dog eating less needs the meal to last longer and feel bigger:

• Low-calorie bulk: green beans, courgette, plain tinned pumpkin

• A slow feeder or puzzle, so the meal takes ten minutes rather than thirty seconds

• Three or four smaller meals rather than two

• A higher-fibre, higher-protein food, which is what veterinary weight-loss diets are formulated to do

The honest bottom line

The arithmetic above is useful, but the two things that actually determine whether a dog stays at a healthy weight are weighing the food and counting the treats.

Everything else is refinement.