Every number here comes from NRC & WSAVA methods and is published as open data (CC BY 4.0). See how we check our numbers →
Underweight dogs need more calories, and calories come from two things: how much you feed and how calorie-dense the food is. A 20 kg dog aiming for 25 kg needs about 1,409 kcal a day — that is roughly 3.1 cups of a 450 kcal/cup food, or 3.5 cups of a 400 kcal/cup one. The food itself matters less than the label number: look for a calorie density above 400 kcal/cup (or 3,800 kcal/kg) and avoid anything labelled light or weight management, which is designed for the opposite problem.
Before any of this: a dog that lost weight without you changing its food needs a veterinarian, not a bigger scoop. Illness, parasites and dental pain all present as weight loss. This page is for a dog that has been checked and now needs to gain.
Four numbers decide whether a food is any good for putting weight on a dog:
| Look for | Why |
|---|---|
| Calorie density ≥ 400 kcal/cup (or ≥ 3,800 kcal/kg) | A dense food means fewer cups for the same calories — which matters for a dog that fills up quickly. |
| Crude protein ≥ 25% | Weight gain should be lean tissue, not only fat. Protein is what builds muscle. |
| Crude fat ≥ 15% | Fat is the most calorie-dense nutrient — it is how a food reaches a high kcal/cup in the first place. |
| Not "light" / "weight management" / "healthy weight" | Those formulas are engineered to be lower calorie. Feeding more of them works, but you are fighting the design. |
| Puppy or "all life stages" | These carry the highest legal nutrient minimums and tend to be the most calorie-dense formulas on the shelf. |
Check the calorie figure on the bag — see how to read a dog food label, and kcal/cup vs kcal/kg for the two ways it is printed.
The amount is set by the target weight, not the current one — calculated at 70 × kg0.75 × 1.8, the clinical weight-gain factor this site uses everywhere.
| Current weight | Target weight | Daily calories | @400 kcal/cup | @450 kcal/cup |
|---|---|---|---|---|
| 10 kg | 12 kg | 812 kcal | 2.0 cups | 1.8 cups |
| 15 kg | 18 kg | 1,101 kcal | 2.8 cups | 2.4 cups |
| 20 kg | 25 kg | 1,409 kcal | 3.5 cups | 3.1 cups |
| 30 kg | 35 kg | 1,813 kcal | 4.5 cups | 4.0 cups |
Run your own numbers in the feeding calculator (set the goal to weight gain), or see the full weight-gain guide for the underlying maths.
1–2% of body weight per week is the usual target. For a 20 kg dog that is 200–400 g a week — faster than that tends to be fat rather than muscle, and puts strain on joints. Weigh monthly, and if the dog stops gaining at the calculated amount, check with your vet before simply adding more.
Do high-calorie foods actually work? Yes, but the arithmetic is what makes them work: you are buying fewer cups per calorie, not more calories per bag. If your dog eats everything you put down, a dense food mainly saves you measuring.
Should I use a puppy food for an adult dog? It is a common and generally safe short-term choice for weight gain — many vets suggest it for exactly this. That said, it is a change of diet, so transition over a week and ask your vet if the dog has any other condition.
My dog will not eat enough of the food. That is the case where calorie density earns its keep — or where the food itself is not the problem and your vet should look for a reason. See weight management for the reverse case; the arithmetic is the same, run backwards.
Looking for a calorie-dense food? Browse high-calorie dog food on Amazon — and check the kcal per cup on any you like against the table above before buying, because the label number is what decides how much you feed.
Want a second option? Browse dry dog food on Chewy — same check applies.
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Sources: the energy equation follows the National Research Council’s Nutrient Requirements of Dogs and Cats (2006); the 1.8× weight-gain factor is clinical practice (not a table row), and this site states it on every weight-gain page. Nutrient minimums follow AAFCO Dog Food Nutrient Profiles. This page is general information, not veterinary advice, and is not a substitute for a diagnosis.
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