Calculate your pet's Resting Energy Requirement (RER) and Maintenance Energy Requirement (MER) using standard veterinary formulas. Essential for nutrition planning, weight management, and calorie calculations.
Quick Answer
RER = 70 × (body weight in kg)0.75 — the same formula for dogs and cats. For daily feeding, multiply RER by your pet's MER factor: 1.2× for low-activity adults up to 3.0× for growing puppies and kittens.
RER is the minimum calories at rest. MER is total daily calories including activity. Use RER as the floor for weight loss; MER for maintenance.
RER = 70 × (weight in kg)0.75
This is the standard veterinary formula for dogs and cats, referenced in AAHA Nutrition & Weight Management Guidelines and WSAVA Global Nutrition Guidelines. RER represents the calories needed at complete rest (base metabolism).
MER = RER × Activity Factor
MER includes calories for normal activity. Typical multipliers:
RER (Resting Energy Requirement) is the calories a pet burns at complete rest — breathing, circulation, organ function, and cell maintenance. MER (Maintenance Energy Requirement) is the total daily calorie need, adding activity, digestion, thermoregulation, and life stage demands on top of RER.
| RER | MER | |
|---|---|---|
| Full name | Resting Energy Requirement | Maintenance Energy Requirement |
| What it measures | Calories at complete rest | Total daily calorie need |
| Formula | 70 × (kg)^0.75 | RER × activity factor |
| Typical range (20 kg dog) | ~639 kcal/day | 767–1,150 kcal/day |
| Use for | Weight loss baseline; hospitalized patients | Daily feeding guidance |
| Never feed below? | Yes — RER is the minimum floor | N/A |
Common RER values by body weight. Find your pet's weight and see their resting calorie needs instantly. MER columns show daily calories at different activity levels.
| Weight | RER (kcal/day) | MER Low (1.2×) | MER Moderate (1.4×) | MER Active (1.8×) |
|---|---|---|---|---|
| 5 lbs (2.3 kg) | 131 | 157 | 183 | 236 |
| 10 lbs (4.5 kg) | 218 | 262 | 305 | 392 |
| 20 lbs (9.1 kg) | 366 | 439 | 512 | 659 |
| 30 lbs (13.6 kg) | 497 | 596 | 696 | 894 |
| 44 lbs (20 kg) | 639 | 767 | 895 | 1,150 |
| 50 lbs (22.7 kg) | 727 | 872 | 1,018 | 1,309 |
| 66 lbs (30 kg) | 848 | 1,018 | 1,187 | 1,526 |
| 70 lbs (31.8 kg) | 935 | 1,122 | 1,309 | 1,683 |
| 100 lbs (45.4 kg) | 1,218 | 1,462 | 1,705 | 2,192 |
Values calculated using RER = 70 × (kg)^0.75. Use the calculator above for exact results with your pet's specific weight.
The RER curve shows how calorie needs scale non-linearly with body weight. A 40 kg dog does not need twice the calories of a 20 kg dog — only about 1.6×. This metabolic scaling (the 0.75 exponent) is why the formula is more accurate than simple per-kg estimates.
kcal/day by body weight. Note the flattening curve — larger pets need proportionally fewer calories per kg.
For dogs, MER multipliers vary by activity level, life stage, and reproductive status. These are standard veterinary guidelines used by the AAHA and WSAVA:
| Dog Status | MER Factor | Notes |
|---|---|---|
| Neutered adult, low activity | 1.2 × RER | Indoor dogs, minimal exercise |
| Intact adult, moderate activity | 1.6 × RER | Regular walks and play |
| Active/working dog | 2.0–5.0 × RER | Herding, hunting, sled dogs |
| Puppy (0–4 months) | 3.0 × RER | Rapid growth phase |
| Puppy (4–12 months) | 2.0 × RER | Continued growth, moderate pace |
| Pregnant (last trimester) | 1.8–3.0 × RER | Increases with litter size |
| Lactating | 3.0–6.0 × RER | Depends on litter size and stage |
| Weight loss | 1.0 × RER | At target weight, vet supervised |
| Senior dog | 1.0–1.4 × RER | Reduced metabolism, adjust individually |
Cats generally have lower activity multipliers than dogs. Indoor cats are particularly prone to obesity because their energy expenditure is much lower than outdoor cats.
| Cat Status | MER Factor | Notes |
|---|---|---|
| Neutered indoor cat | 1.0–1.2 × RER | Sedentary indoor lifestyle |
| Intact adult cat | 1.2–1.4 × RER | Slightly higher metabolism than neutered |
| Active outdoor cat | 1.4–1.6 × RER | Hunting, exploring, temperature regulation |
| Kitten (0–4 months) | 2.5 × RER | Rapid growth phase |
| Kitten (4–12 months) | 2.0 × RER | Continued growth, slightly less than young kitten |
| Pregnant cat | 1.6–2.0 × RER | Increases through pregnancy |
| Lactating cat | 2.0–6.0 × RER | Depends on litter size, free-feed recommended |
| Weight loss | 0.8 × RER | At target weight, vet supervised — never fast a cat |
| Senior cat (11+ years) | 1.0–1.1 × RER | Reduced activity, monitor weight closely |
The RER formula is the same for cats as for dogs — RER = 70 × (kg)^0.75 — but cat-specific considerations matter:
For a complete daily calorie plan for your cat, use our Cat Calorie Calculator, which accounts for food type, brand, and body condition score.
Growing animals need significantly more energy than adult pets of the same weight. The RER formula still applies, but MER multipliers are much higher during growth phases.
Puppies aged 0–4 months use 3.0× RER — they're in rapid growth and need triple their resting energy. From 4–12 months, this drops to 2.0× RER as growth slows. After 12 months (or when they reach ~80% of adult size), transition to the appropriate adult multiplier.
Large and giant breeds (e.g., Great Danes, Mastiffs) should be kept on the lower end of their growth-phase MER and fed breed-appropriate puppy food to avoid overly rapid bone growth, which can contribute to orthopedic disease. See our Dog Calorie Calculator or breed-specific weight calculators for growth targets.
Kittens aged 0–4 months use 2.5× RER. From 4–12 months, this drops to 2.0× RER. After 12 months, most cats settle into the neutered indoor adult range of 1.0–1.2× RER.
Kittens should be fed kitten-specific food (higher protein, higher fat, plus taurine supplementation) during growth phases. Free-feeding is generally acceptable for healthy kittens since they tend to self-regulate until around 6 months. For a full calorie guide, see our Cat Calorie Calculator.
RER and MER calculations provide a starting point for calorie planning. Every pet is different — monitor your pet's weight and body condition score every 2–4 weeks and adjust portions accordingly. Consult your veterinarian for personalized feeding plans, especially for weight loss, pregnancy, growth phases, or medical conditions.
For a complete daily calorie plan based on your pet's specific factors, use our Dog Calorie Calculator or Cat Calorie Calculator. For weight management, see the Dog Weight Loss Calculator or Cat Weight Loss Calculator. For puppy nutrition, see the Puppy Calorie Calculator.
References
FAQs
RER is the number of calories a pet needs at complete rest — the base metabolic rate. It's calculated using the formula: RER = 70 × (weight in kg)^0.75. This is the minimum energy needed for basic bodily functions like breathing, circulation, and organ function.
MER is the total daily calories a pet needs including normal activity. It's calculated by multiplying RER by an activity factor (typically 1.2–2.0 depending on activity level, life stage, and reproductive status).
RER is the calories a pet needs at complete rest (base metabolism only). MER is higher — it includes RER plus the energy needed for normal daily activity, digestion, thermoregulation, and other metabolic processes. For most adult dogs, MER is 1.2–1.6× RER. Use RER as the baseline for weight loss calculations; use MER for maintenance feeding.
Use our RER calculator above. Enter your pet's weight in pounds or kilograms, and we'll calculate RER using the formula: RER = 70 × (weight in kg)^0.75.
The RER formula is: RER = 70 × (weight in kg)^0.75. This is the standard veterinary formula for calculating resting energy requirements in dogs and cats, recommended by the AAHA and WSAVA nutritional guidelines.
MER is calculated by multiplying RER by activity and life stage factors. For example: Low activity (neutered indoor dog) = RER × 1.2, Moderate activity = RER × 1.4–1.6, High activity/working dog = RER × 2.0–5.0. Puppies and kittens need higher multipliers (2.0–3.0×).
For a 10 kg (22 lb) dog: RER = 70 × (10)^0.75 = 70 × 5.62 = 394 kcal/day. At moderate activity (1.4× multiplier), MER would be about 551 kcal/day. Puppies, pregnant, or nursing dogs need higher multipliers.
For a 5 kg (11 lb) cat: RER = 70 × (5)^0.75 = 70 × 3.34 = 234 kcal/day. A neutered indoor cat (1.2× multiplier) needs about 281 kcal/day MER. Active outdoor cats may need 1.4× or about 328 kcal/day.
Yes. The RER formula — RER = 70 × (body weight in kg)^0.75 — is the same for both dogs and cats. The difference is in MER multipliers: dogs typically use higher activity factors (1.2–2.0+) while indoor cats use lower factors (1.0–1.4). Kittens and puppies in growth phases both require significantly higher multipliers (2.0–3.0×).
For weight loss, calculate RER at the target weight (not current weight) and use a reduced MER multiplier — typically 1.0× RER for dogs, 0.8× for cats. Never feed below RER without veterinary supervision. A safe weight loss rate is 1–2% of body weight per week. Note: Never fast a cat — hepatic lipidosis (fatty liver disease) can develop rapidly.
A kitten aged 4–12 months uses a MER factor of 2.0× RER. Younger kittens (0–4 months) in the rapid growth phase use 2.5× RER. After 12 months, transition to the adult multiplier for your cat's lifestyle (1.0–1.4× for indoor cats).
The RER formula (70 × kg^0.75) accounts for metabolic scaling — larger animals have proportionally lower metabolic rates per kilogram. The 0.75 exponent (metabolic body weight) accurately reflects this non-linear relationship across all body sizes, from a 1 kg kitten to a 60 kg Great Dane.
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