PetCalcCare Planning
HomeGuidesMetabolic Math: Portion Sizes & Caloric Balance
Pet Care Guide

Metabolic Math: Portion Sizes & Caloric Balance

Calculate Resting Energy Requirement (RER) and adjust for activity factors to avoid joint strain and combat pet obesity.

July 3, 2026

Combating the Pet Obesity Epidemic

Pet obesity is a widespread clinical health issue. Excess weight strains joints, exacerbates osteoarthritis, raises blood pressure, and contributes to endocrine conditions like feline diabetes. Maintaining your pet at an ideal weight is one of the most effective ways to add healthy years to their lifespan.

The RER Formula & Activity Adjustments

To feed your pet scientifically, you must first calculate their Resting Energy Requirement (RER) — the calories required for fundamental organ function at rest. This is calculated as:

RER = 70 × (Weight in kg)0.75

This base RER is then multiplied by an activity factor (usually 1.2 to 1.6 for neutered house pets, and up to 3.0 for working, pregnant, or growing animals) to determine their Daily Energy Requirement (DER).

Measuring Treats Responsibly

Ensure that commercial treats and table scraps make up less than 10% of your pet's daily calorie budget. The remaining 90% must come from a complete, nutritionally balanced diet to avoid vitamin deficiencies.