Sources and methodology

Calorie and feeding calculations

All calorie calculations use the Resting Energy Requirement (RER) formula: RER = 70 x (body weight in kg)^0.75. The RER is multiplied by a Maintenance Energy Requirement (MER) factor that varies by species, life stage, activity level, and reproductive status.

This formula comes from the National Research Council's Nutrient Requirements of Dogs and Cats (2006), published by the National Academies Press. It is the standard reference used by veterinary nutritionists worldwide.

Feeding portions are calculated by dividing daily calorie needs by the caloric density of the specific food (kcal per cup or kcal per kg), which the user provides.

Primary sources

• National Research Council. Nutrient Requirements of Dogs and Cats. Washington, DC: The National Academies Press, 2006.
• Merck Veterinary Manual. "Nutritional Requirements of Dogs" and "Nutritional Requirements of Cats." Merck & Co., continuously updated.
• Ohio State University, College of Veterinary Medicine. Companion Animal Nutrition Support Service: Basic Calorie Calculator.

Breed weight and size data

Dog breed weight ranges, height ranges, and size classifications come from the American Kennel Club (AKC) official breed standards. Each breed's parent club defines the standard, which the AKC approves.

Cat breed weight and size data come from The International Cat Association (TICA) and Cat Fanciers' Association (CFA) breed profiles.

Where AKC/TICA standards provide a range (e.g., "55-70 lbs"), we use those ranges directly. Calorie estimates on breed pages use the midpoint of the male and female weight ranges to calculate a representative daily calorie need.

Primary sources

• American Kennel Club (AKC). Individual breed standards. akc.org/dog-breeds/
• The International Cat Association (TICA). Individual breed profiles. tica.org/breeds/
• Cat Fanciers' Association (CFA). Breed profiles and standards. cfa.org/breeds/

Age conversion

Dog age conversion uses two methods displayed together. The primary method is the AVMA size-adjusted formula, which accounts for the fact that large dogs age faster than small dogs. The secondary method is the epigenetic (DNA methylation) formula from UC San Diego research, calculated as: human age = 16 x ln(dog age) + 31.

Life stage classification follows the AAHA 2019 Canine Life Stage Guidelines, which define puppy, young adult, mature adult, and senior stages based on breed size.

Cat age conversion uses the AAFP/AAHA Feline Life Stage Guidelines.

Primary sources

• Wang, T., et al. "Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome." Cell Systems, vol. 11, no. 2, 2020, pp. 176-185.
• American Veterinary Medical Association (AVMA). "How to Calculate Your Dog's Age."
• American Animal Hospital Association (AAHA). "2019 AAHA Canine Life Stage Guidelines."
• American Association of Feline Practitioners (AAFP). "Feline Life Stage Guidelines."

Body condition scoring

The ideal weight tool uses the body condition scoring (BCS) system to assess whether a pet is underweight, ideal, or overweight. This is the same 9-point scale used in veterinary clinics worldwide.

Primary sources

• World Small Animal Veterinary Association (WSAVA). "Body Condition Score Charts" for dogs and cats.
• Association for Pet Obesity Prevention (APOP). Pet obesity statistics and BCS references.

Health condition data

Breed-specific health predispositions listed on breed profiles come from AKC breed health statements, the Canine Health Information Center (CHIC), and published veterinary literature. These are general predispositions, not diagnoses. Individual dogs and cats vary.

The Cambridge University POMC gene research cited on Labrador Retriever and related breed pages refers to: Raffan, E., et al. "A Deletion in the Canine POMC Gene Is Associated with Weight and Appetite in Obesity-Prone Labrador Retriever Dogs." Cell Metabolism, vol. 23, no. 5, 2016, pp. 893-900.

Data verification

All breed data, calorie formulas, and source links are reviewed periodically. Each page displays a "Last reviewed" date showing when its data was last verified against primary sources.

If you find an error or an outdated data point, please email hello@breedlookup.com.

Last full data review: April 1, 2026.