Pet Calorie Needs (RER / MER) Calculator
Calculate your dog or cat’s daily calorie needs with the veterinary RER and MER formulas, adjusted for life stage and activity.
How it works
RER = 70 × weight(kg)^0.75 · MER = RER × life-stage factor
The Resting Energy Requirement uses an allometric power law — 70 times body weight in kilograms to the ¾ power — because metabolism does not scale linearly with size; a dog twice as heavy needs less than twice the calories. Multiplying RER by a life-stage factor gives the Maintenance Energy Requirement, the real daily target: about 1.6 for a neutered adult, up from RER for growth or work and down toward RER itself for weight loss. Feed to the MER, then adjust by watching body condition over a few weeks.
Worked example
A 10 kg neutered adult dog has RER = 70 × 10^0.75 = 70 × 5.62 ≈ 394 kcal. At a ×1.6 maintenance factor, MER ≈ 394 × 1.6 = 630 kcal per day.
Frequently asked questions
What is the difference between RER and MER?
RER is the calories a pet burns completely at rest, purely to stay alive. MER (Maintenance Energy Requirement) multiplies that by an activity/life-stage factor to cover movement, digestion, growth or reproduction — it is the number you actually feed to.
Why the ¾ power instead of just weight?
Smaller animals burn more calories per kilogram than larger ones, a relationship biologists call allometric scaling. Raising weight to the 0.75 power captures that, so the estimate stays accurate across a Chihuahua and a Great Dane rather than only near one size.
How do I use this for weight loss?
For a slimming plan, calculate MER using the pet’s ideal (target) weight and the ×1.0 weight-loss factor, not its current heavier weight. Then reassess body condition every couple of weeks and adjust.
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Educational estimate only — not veterinary advice. Always consult a licensed veterinarian before dosing, treating, feeding, or making care decisions for any animal.