Half of American dogs carry extra weight, and the most common cause isn't the wrong food. It's the right food, measured wrong. Here's the RER formula vets actually use, a feeding table by weight, and how to translate calories into cups for whatever bag you're pouring from.
Veterinary nutrition starts from the resting energy requirement, or RER: the calories a dog burns doing nothing but existing. The equation is RER = 70 x (weight in kg)^0.75. The 0.75 exponent is the interesting part. It's Kleiber's law, and it means a 100 lb dog doesn't burn ten times what a 10 lb dog burns. It burns about 5.6 times more, because bigger bodies run more efficiently per pound.
Then a multiplier covers life stage. The standard factors, drawn from the charts used by veterinary nutrition centers like Ohio State's and published in the Merck Veterinary Manual:
Many vets also dial seniors down toward 1.4 as metabolism slows. Skip the guessing and run your dog's exact numbers in the dog food calculator, which converts pounds to kilograms, applies the factor, and turns the result into cups once you enter your food's kcal per cup.
Here's the table for the common weights, computed with the formula above:
| Weight | RER (kcal) | Neutered adult (x1.6) | Intact adult (x1.8) | Puppy <4 mo (x3.0) |
|---|---|---|---|---|
| 10 lb | 218 | 348 | 392 | 653 |
| 20 lb | 366 | 585 | 659 | 1,098 |
| 30 lb | 496 | 794 | 893 | 1,488 |
| 50 lb | 727 | 1,164 | 1,309 | 2,182 |
| 70 lb | 936 | 1,498 | 1,685 | 2,809 |
| 100 lb | 1,223 | 1,958 | 2,202 | 3,670 |
One worked example so the formula isn't a black box. A 30 lb beagle mix weighs 13.6 kg. RER = 70 x 13.6^0.75 = 496 kcal. She's spayed, so 496 x 1.6 = 794 kcal a day. That's the whole calculation.
Find the kcal per cup on your bag. It's legally required on the label, usually near the guaranteed analysis, written like "3,746 kcal ME/kg; 381 kcal ME/cup." Most dry foods run 350 to 450 kcal per cup, but the range across brands stretches from about 300 to 500, and that spread quietly explains why switching foods without recalculating makes dogs gain weight.
Back to the beagle: 794 kcal on a 375 kcal/cup food is 2.1 cups a day, about a cup per meal. The same dog on a 450 kcal/cup rich formula gets 1.8 cups, and on a 320 kcal/cup light food gets 2.5. Cups are a unit of volume, not nutrition, which is why the calorie number has to come first.
If you feed wet food, the same math applies with kcal per can or kcal per gram. And if you like precision, a $12 kitchen scale plus the bag's kcal per kg beats any cup: grams x kcal/kg / 1000 = calories.
Enter weight, life stage, and your bag's kcal per cup. See daily kcal, cups per day, and a treat allowance.
Dog Food Calculator →Usually because mealtime is the best part of the day and dogs are excellent actors. Medically, though, conditions like Cushing's, diabetes, and hypothyroidism all raise appetite, so a genuinely ravenous dog with weight changes deserves a vet visit before a bigger scoop.
Behaviorally, you can blunt begging without adding calories: split the same daily total into more, smaller meals, reserve part of the k ration as training treats, or add a few tablespoons of plain green beans or pumpkin to the bowl. Volume up, calories flat.
Feed RER at the target weight with the 1.0 factor. Take an 80 lb dog whose healthy weight is 65 lb. RER at 65 lb (29.5 kg) is 70 x 29.5^0.75 = about 886 kcal. That's the daily ration, even though the dog currently weighs 80 lb, where a maintenance ration would be 1,656 kcal. The gap is the point: it's a diet.
Target 1 to 2 percent of body weight lost per week and weigh every two weeks. Faster losses burn muscle and can trigger nutrient deficiencies. Slower means the treat budget is leaking somewhere, and the usual suspects are dental chews (some run 80+ kcal each) and "just a few" kibbles handed out a dozen times a day.
Keep the arithmetic honest with a human calorie tool like our calorie calculator mentality applied to the dog: total calories in, including every treat, versus the daily target. If you're tracking protein during weight loss to protect lean mass, the same discipline shows up in the protein intake calculator.
The scale answer to "how much should I feed my dog" is a starting point, not a law. Your dog's ribs are the scoreboard: you want to feel them easily under a thin layer of fat, see a waist from above, and a tuck from the side. That's a body condition score of 4 to 5 out of 9, and hitting it beats any formula's output by a mile. For anything beyond routine tweaks (a weight-loss plan, a senior with kidney values creeping up, a growing giant breed puppy), run the numbers with your vet.
Divide daily calories by your food's kcal per cup. A 30 lb neutered dog needs about 794 kcal a day; on a 375 kcal/cup food that's 2.1 cups, or roughly one cup per meal twice a day. On a 450 kcal/cup food the same dog gets 1.8 cups, which is why the bag matters more than the breed chart.
Bag charts are calibrated to keep a typical active dog lean and err generous, since underfeeding complaints are worse for a food brand than slow weight gain. Vets calculate from RER and body condition instead. If the chart and your vet disagree, follow the vet, then confirm with a body condition score of 4 to 5 out of 9 two or three weeks in.
Calculate RER at the target weight, not the current one, using a factor of 1.0. A dog that should weigh 65 lb gets about 886 kcal a day, even if it currently weighs 80 lb. Re-weigh every two weeks and aim to lose 1 to 2 percent of body weight per week; faster loss risks muscle loss and nutrient gaps.