How much should my dog eat? The RER/MER formula, explained

PetCost Editorial Team · Figures cross-checked against NAPHIA, AKC and veterinary RER/MER guidance · Updated 2026-06-08

Feeding guidelines on the bag are averages. Here's the actual vet formula for your dog's calories — and how it translates into cups per day and dollars per year.

How many calories does your dog need?

A dog's energy need scales with metabolic body weight, not linearly — which is why a dog twice as heavy doesn't eat twice as much. Using the veterinary RER/MER formula for a typical neutered adult (activity factor 1.6), here's how daily calories rise with weight:

Notice the curve flattens: a 100 lb dog needs roughly 4–5× the calories of a 10 lb dog, not 10×.

Feeding chart: calories, cups and cost by weight

The table below runs the full calculation for a typical adult dog on standard dry food (~340 kcal per cup, priced around $2.50/lb). Find your dog's weight for a realistic daily portion and monthly food bill — then fine-tune for activity and life stage below.

Calories from the RER/MER formula; cups assume ~340 kcal/cup; cost assumes ~$2.50/lb dry food. Your food's label and price will shift the dollar figure — this is exactly the calculation behind every breed page.

The formula vets use

RER (Resting Energy Requirement) = 70 × (body-weight-in-kg)^0.75. Multiply by a MER (Maintenance Energy Requirement) factor — about 1.2–1.4 for inactive or senior dogs, 1.6 for a typical neutered adult, and 2.0–5.0 for very active, working, pregnant or lactating dogs. That gives daily calories. Divide by your food's kcal-per-cup (commonly ~340 for dry food) to get cups per day.

Puppy, adult, senior: how needs change

Life stage is a bigger swing than most owners realize. Puppies need roughly 2× an adult's per-pound calories while growing (often fed 3× the RER under ~4 months, ~2× from 4 months to maturity). Adults sit at the 1.6 maintenance factor. Seniors typically slow down and need 10–20% fewer calories — feeding a 9-year-old like a 3-year-old is a common cause of slow weight gain. Always shift portions gradually and re-check body condition monthly.

Activity level changes everything

Two dogs of identical weight can differ by 50%+ in daily calories based on activity. Match the MER multiplier to real life:

A weekend of heavy exercise doesn't justify a permanent portion bump — feed for the dog's average week.

Wet vs dry: portion and cost

Wet food is far less calorie-dense (~70–90 kcal per 3 oz vs ~340 per cup of dry), so the same dog eats a much larger volume of wet food — and usually pays more per calorie. Mixing the two means re-running the calorie math for each: feed enough of each to hit the same daily kcal total, not the same number of cups and cans.

The 10% treat rule

Treats, chews and table scraps should make up no more than 10% of daily calories — the rest comes from balanced food. For a 30 lb dog needing ~700 kcal, that's only ~70 kcal of treats (a couple of small biscuits). Treats are the most common hidden source of weight gain because they're rarely counted; subtract them from the meal allowance, don't add them on top.

Signs you're over- or under-feeding

Trust the body condition score over the bag. You should be able to feel (but not see) the ribs with light pressure, see a visible waist from above, and a tucked-up belly from the side. No waist and hard-to-feel ribs = overfeeding; visible ribs, spine and hip bones = underfeeding. Re-weigh monthly and adjust portions by 10% at a time rather than guessing.

How often should you feed?

Most adult dogs do best on two meals a day, roughly 8–12 hours apart, which steadies energy and reduces bloat risk in deep-chested breeds. Puppies need 3–4 smaller meals; very small breeds may need more frequent feeding to avoid low blood sugar. The total daily calories matter more than the number of meals — splitting the same amount across two bowls doesn't change the math.

Why bag guidelines mislead

Bag charts assume an 'average' dog and often over-portion, contributing to canine obesity (a leading driver of vet costs). The RER/MER calculation is individualized to weight and activity. Always adjust for body condition and confirm with your vet, especially for puppies, seniors or pregnant dogs.

From cups to dollars

Multiply cups per day by 30 to get monthly volume, convert to pounds, and price at your food's cost per pound. This is exactly how we compute every breed's food cost — see the live figure and a cumulative-over-lifetime chart on any breed page, or rank breeds by how much they eat.

FAQ

How many calories does my dog need per day?

Use RER = 70 × (weight-in-kg)^0.75, then × 1.6 for a typical adult. Roughly: 10 lb ≈ 350 kcal, 30 lb ≈ 720 kcal, 50 lb ≈ 1,050 kcal, 90 lb ≈ 1,650 kcal.

How many cups should I feed my dog?

Roughly 0.5–1 cup of dry food per 10 lb of body weight per day for a typical adult — calculate precisely by dividing daily calories (MER) by your food's kcal-per-cup (commonly ~340).

Should I feed my puppy more than an adult dog?

Yes — growing puppies need about twice the per-pound calories of an adult (often 2–3× the RER), then taper to the adult amount as they reach full size.

How much should I feed an active or working dog?

Raise the MER factor from 1.6 up to 2.0–5.0 depending on workload, but feed for the dog's average week, not its busiest day.

How many times a day should I feed my dog?

Two meals a day suits most adult dogs; puppies need 3–4. Meal count doesn't change total calories — split the daily amount, don't add to it.

How is dog food cost calculated?

From body weight via the RER/MER calorie formula, converted to cups, then pounds, then priced at the food's cost per pound — the method behind every breed page here.

How do I know if I'm overfeeding?

Use body condition: ribs should be easy to feel but not see, with a visible waist from above. No waist and hard-to-feel ribs means cut portions by ~10%.

Which dogs eat the most?

The largest breeds — intake scales with metabolic body weight. See our 'dogs that eat the most' ranking.

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