RER Calculator (Resting Energy Requirement)
Calculate your dog or cat's Resting Energy Requirement -- the baseline calorie number used in every veterinary feeding formula.
Awaiting Details
Enter your pet's weight to see their RER.
The RER Formula
Resting Energy Requirement is the standard veterinary formula for baseline metabolic calorie needs, based on Kleiber's law relating metabolic rate to body mass:
RER is a resting baseline, not a feeding amount. To get your pet's actual daily feeding target, this number is multiplied by a life-stage and activity factor to produce the Maintenance Energy Requirement (MER) -- see our MER Calculator.
Frequently Asked Questions
What is Resting Energy Requirement (RER)?
RER is the number of calories a dog or cat needs at complete rest in a thermoneutral environment, to fuel basic body functions like breathing, circulation, and cell repair. It's the baseline every other calorie calculation (MER, weight-loss, weight-gain targets) is built from.
Is RER the same as how much I should feed my pet?
No. RER is a resting baseline, not a feeding target. Actual feeding amounts (Maintenance Energy Requirement, or MER) multiply RER by a life-stage and activity factor -- use our MER Calculator or Calorie Calculator for that number.
Why is the formula a power of 0.75 instead of linear?
Metabolic rate doesn't scale directly with body weight -- it scales with weight to the 3/4 power, a relationship (Kleiber's law) that holds broadly across mammals and is the basis for the standard veterinary RER formula.
Does RER differ between dogs and cats?
The RER formula itself (70 × weight in kg^0.75) is the same for both species -- it's the multipliers used for MER (activity, life stage, spay/neuter status) that differ between dogs and cats.
Medical Disclaimer
This tool provides general, educational estimates and is not a substitute for professional veterinary advice, diagnosis, or treatment. RER is a baseline metabolic estimate, not a feeding recommendation. Use the MER Calculator or Calorie Calculator to determine actual feeding amounts. Always consult your veterinarian about your pet's specific health needs before making changes to their diet, water intake, or care routine.
Related Tools
MER Calculator
Convert RER into an actual daily feeding calorie target.
Calorie Calculator
Find your pet's daily calorie needs based on weight and activity.
Food Portion Calculator
See how many cups or grams to feed per day.
Daily Macronutrient Calculator
Estimate daily protein, fat, and carbohydrate needs.
How This Calculator Works
Read the full breakdown of the formula, sources, and how to interpret your result.