How much to feed your dog, by weight

A 10 kg neutered dog needs about 630 kcal a day by the Merck Veterinary Manual's formula. On a food with 3,500 kcal per kilo, that's 180 g. A 30 kg dog needs about 1,436 kcal, or 410 g, so three times the weight doesn't mean three times the food.

That's the useful surprise here. I worked these sums from the formula, store labels and named sources, and no dog was weighed for them. They cover healthy adults. For a puppy, a pregnant dog, an illness or a diet your vet has set, ask the vet.

The formula is 70 x kg^0.75, multiplied by 1.6 for a neutered adult and 1.8 for an intact one. The 3,500 is a round figure for the example, so swap in your own bag's. For why the neutered column runs lower, see do neutered pets need less food?

Six steps to a daily portion

1. Weigh the dog. Use the scales at the vet's or, for a dog you can lift, stand on bathroom scales with and without it. A guess of the breed's average won't do: PDSA's average for a Labrador alone spans 25 to 35 kg.
2. Read the table for your bag. The zooplus page for Royal Canin Mini Adult gives a 4 kg dog 69 g on reduced activity, 80 g on normal and 91 g on high. Pick your row honestly. Most of us overrate our walks.
3. Find the calories. The store states 3,916 kcal/kg for that food. If your bag gives kcal per 100 g, multiply by 10.
4. Run the sum as a check. Take the kcal from the formula above, divide by the kcal per kilo, multiply by 1,000. A 4 kg neutered dog needs 317 kcal, which is 81 g of this food and sits right beside the page's 80 g. Tables don't always agree so neatly. Zooplus's table for Pedigree Adult Complete gives 345 to 380 g for a 30 kg dog, where the formula gives 407 g. When the two differ, I'd start at the lower one and watch the dog.
5. Weigh the portion. The tables are in grams, so use kitchen scales. Then take treats off the total: the Pedigree page says to account for the calories from them. On meals, sources differ. Battersea says dogs should typically eat at least two a day, and the RSPCA says at least once a day unless your vet advises otherwise.
6. Check the dog's shape. PDSA's Body Condition Score method uses your hands and eyes. You should feel the ribs with a light touch, feel the spine and hipbones without seeing them, and see a waist from the side and from above. Merck says one animal may need as much as 30% more or fewer calories than another of the same weight, and Ohio State University's vet centre says as much as 50% from the calculated value. If the shape drifts, change the portion a little. If you're unsure what the target is, ask your vet, since PDSA names the vet as the best person to ask.

What that portion costs

Back to the 4 kg dog. At 317 kcal a day and 3,916 kcal/kg, a year comes to 29.5 kg of food, between seven and eight 4 kg bags. At £23.89 a bag, read on 2 November 2026, that's about £176 before delivery.

Bigger bags and other foods shift it a lot, and kilos are a poor way to compare them. Price per 1,000 kcal does that job. Or put your dog's weight into the pet cost calculator and overwrite what doesn't fit.