Home › Guides › Pet Nutrition

How Much Should You Feed Your Dog? RER, MER and Working Out Calories

Updated October 21, 2026 · By the PureOrganism editors

The feeding guide on a bag of dog food is a starting point written for an average dog. Your dog is not average. The same 20 kg labrador-cross can be a lean, active working dog or a sofa-loving, neutered, slightly round one, and their daily energy needs can differ by a third or more. Veterinary nutritionists handle this with a short calculation that is simple enough to do on a phone: first estimate resting energy requirement (RER), then multiply by a factor that reflects the dog's life stage and lifestyle to get a maintenance energy requirement (MER).

This article walks through that calculation with worked examples, shows how to turn calories into a measured portion, and explains how to adjust using body condition rather than the arithmetic alone. It is general information compiled by the site editors and is not veterinary advice. The editors are not veterinarians. A dog with a medical condition, a very young puppy, a pregnant or nursing dog, or one that needs to lose a lot of weight should have a feeding plan from a vet.

RER: the resting baseline

RER is the energy a healthy animal at rest in a comfortable environment needs to keep its body functioning. The most widely used formula in veterinary nutrition is:

RER (kcal per day) = 70 × (body weight in kg)^0.75

The exponent 0.75 reflects the fact that energy needs do not rise in a straight line with weight. A dog twice as heavy does not need twice the calories, because metabolic rate scales more slowly than body mass. A veterinary nutrition presentation drawing on the World Small Animal Veterinary Association (WSAVA) resources gives this exponential form as preferred, and notes that the simpler linear shortcut is inaccurate at extreme body weights.

That linear shortcut, which you will see in some guides, is 30 × body weight in kg + 70. It is a reasonable approximation for dogs between roughly 2 and 45 kg and can be done without a scientific calculator. For the examples below, we compare both.

To use the exponential form on a phone, enter the weight, press the power key, and raise it to 0.75, then multiply by 70. You can also check your result with our dog energy calculator.

MER: from resting to real life

RER is not what a dog eats. A dog that walks, plays, digests food and keeps itself warm needs more. MER is RER multiplied by a factor. Veterinary nutrition texts list a range of factors, and the exact numbers vary slightly between sources, so treat the following as typical starting points rather than rules.

The editors looked for a primary WSAVA source for these exact multipliers and could not confirm a single authoritative table, so the numbers above should be read as common rules of thumb rather than a guideline from any one body. The neutered-adult figure of 1.6 and the intact-adult figure of 1.8 are widely published, and many calculators use them. The WSAVA Global Nutrition Committee's nutrition guidelines are the place to start if you want the professional framework.

A worked example, with every step

Imagine a neutered adult dog weighing 20 kg with ordinary daily walks. This is an example, not a recommendation for your dog.

1. RER: 70 × 20^0.75. Since 20^0.75 is about 9.46, RER is about 662 kcal per day.
2. MER: 662 × 1.6 = about 1,059 kcal per day.
3. Food energy: read the bag. Suppose the label says 3,600 kcal of metabolisable energy (ME) per kilogram, which is also 3.6 kcal per gram. These are example numbers.
4. Daily weight of food: 1,059 ÷ 3.6 = about 294 g per day.
5. Per meal: over two meals, about 147 g each.

If the label gives kcal per cup instead, say 360 kcal per cup, then 1,059 ÷ 360 is about 2.9 cups per day. But a cup is not a standard unit; it varies from kibble to kibble, and from scoop to scoop, so weigh the food on kitchen scales for a few days to calibrate your cup.

Notice what happened to the treats. Any food outside the meals counts toward the 1,059 kcal. It is common in veterinary and nutrition guidance to keep treats and extras to about 10% of daily calories, which here would be roughly 105 kcal, and to reduce the main meal by the same amount. A single large dental chew can use up a big share of that.

Reading the label correctly

• Look for the energy statement. In the US, labels show kcal per kg and per cup (or can). In the UK and EU, energy is often shown in kcal or MJ per kg, and you may see "metabolisable energy" in the analysis.
• Do not compare feeding tables across brands. A calorie-dense food needs a smaller portion than a lighter one; the guide on the bag is calibrated to that bag.
• Check that the food is "complete" for the life stage. Complementary foods are not designed to be the whole diet.
• Calories from wet food count. If you mix wet and dry, calculate each and reduce the dry portion accordingly.

Calories are the start; body condition is the answer

RER and MER are estimates for a population. Individual dogs vary in metabolism, muscle mass, age, coat, climate and activity, so two dogs of identical weight can need noticeably different amounts. The reliable check is how your dog looks and feels.

Vets use a body condition score (BCS), usually on a 9-point scale where 4 to 5 is ideal. WSAVA publishes a body condition chart for dogs. In general terms:

• You should be able to feel the ribs easily under a thin layer of fat, without pressing hard.
• From above, there should be a visible waist behind the ribs.
• From the side, the belly should tuck up toward the hind legs.

If your dog is heavier than the chart suggests, do not reduce food drastically and do not rely on a formula alone. Weight-loss diets for dogs are usually set by a vet, using a target weight and regular weigh-ins, and the calculation is based on ideal weight, not current weight.

A practical monitoring routine

1. Weigh your dog on the same scales every two to four weeks. For a small dog you can weigh yourself with and without the dog; for a bigger dog many vets' reception areas have scales you can use.
2. Score body condition at the same time, using the chart.
3. If weight and condition are stable, keep going. If weight is creeping up, trim the daily total by a small amount, about 5 to 10%, and recheck in a few weeks. If your dog is losing weight without trying, check with a vet rather than just adding food.
4. Update the calculation when something changes: neutering, a move to a senior life stage, a new exercise routine, or a change of food.

When the formula is not enough

• Puppies. They grow quickly, and large-breed puppies need controlled growth to protect joints. Use a puppy-specific food and the manufacturer's guide, and talk to a vet about the plan.
• Pregnant and nursing dogs. Needs rise significantly. Ask a vet.
• Medical conditions. Kidney disease, diabetes, pancreatitis, heart disease and others may require specific diets and portions.
• Very small or very large dogs. The linear shortcut becomes less reliable at the extremes, which is one reason the exponential formula is preferred.
• Extremes of weather. Cold-weather outdoor dogs may need more, and hot weather may reduce appetite.
• Underweight rescue dogs. They often need gradual refeeding under veterinary guidance.

Common mistakes

• Using current weight in the formula for an overweight dog and calling it a diet.
• Counting a cup as a fixed quantity without weighing it.
• Forgetting treats, chews, dental sticks, training rewards and table scraps.
• Free-feeding a dog that eats whenever food is available.
• Copying the number from a friend's dog of the same breed.
• Believing the bag's feeding table is a legal or clinical standard. It is a manufacturer's guide.

Common questions

Why does my dog seem hungry on the calculated amount?

Hunger is not always about calories. Check that the portion is weighed accurately, consider splitting the day into more meals, and use low-calorie extras such as a portion of the daily allowance saved for training. If your dog seems unusually hungry and thirsty, mention it to a vet.

Does neutering change the numbers?

Neutered dogs generally need fewer calories on average, which is why the typical factor is lower than for intact dogs. Watch condition after surgery and adjust.

Should I feed once or twice a day?

Many adult dogs do well on two meals. This is a management preference, not a calorie issue; ask your vet if your dog has a medical reason to change.

Sources

• WSAVA: Global Nutrition Guidelines
• WSAVA: Body Condition Score chart for dogs
• Canadian Veterinary Medical Association conference proceedings (2016): Nutritional assessment

Not veterinary advice. The authors are not veterinarians. If your pet may have eaten something toxic, call your vet or a pet poison line now: ASPCA Animal Poison Control (US) +1 888-426-4435, Pet Poison Helpline (US/Canada) +1 855-764-7661, Animal PoisonLine (UK) 01202 509000. Fees may apply. Spotted a mistake? Email huhuwen09@gmail.com with the page address and we will check and correct it.