How we calculate
Every calculator uses a published formula or guideline, listed below and on each page. All results are estimates for general information. No calculator replaces your veterinarian.
Dog age
- Size-based chart: the widely published year-by-year table by size (its medium column matches the AKC guideline of 15, then 9, then about 5 a year), for example 10 dog years = 56 (small), 60 (medium), 66 (large) or 79 (giant) human years; we interpolate between whole years. Size classes are by adult weight: small under 20 lb (9 kg); medium 20–50 lb (9–23 kg); large 51–100 lb (23–45 kg); giant over 100 lb (45 kg). Different publishers use slightly different values; ours is a widely used version.
- UCSD formula: human age = 16 × ln(dog age) + 31, from a 2020 study of DNA methylation in Labrador Retrievers. We use it for dogs of 3 months and older.
- Life stage: puppy until about 1 year (1.5 for large and 2 for giant breeds); senior over the last quarter of the typical lifespan (small 14 years, medium 12 years, large 10.5 years, giant 8.5 years), following the AAHA approach. Breed pages use the breed's own typical lifespan.
Cat age
15 human years for the first year, 24 for the second, then 4 per year. Life stages follow the AAFP and AAHA guidelines: kitten to 1 year, young adult 1–6, mature adult 7–10, senior over 10.
Food
Resting energy requirement (RER) = 70 × (kg)0.75 kcal per day (NRC 2006). Daily energy is RER times a life stage factor.
Dogs: adult, neutered or spayed ×1.6; adult, not neutered ×1.8; adult, inactive or prone to weight gain ×1.4; weight loss (use ideal weight) ×1; puppy under 4 months ×3; puppy 4 months to adult size ×2; senior ×1.4; very active or working ×2.
Cats: adult, neutered or spayed ×1.2; adult, not neutered ×1.4; adult, inactive or prone to weight gain ×1; weight loss (use ideal weight) ×0.8; kitten (growing) ×2.5; senior ×1.1; very active ×1.6.
Amounts of food are calculated from the calories you enter from your food's label. We do not guess a food's energy density. Pregnant, nursing, ill or very overweight pets need a vet's plan.
Pregnancy
Dogs: 63 days from ovulation, 65 days from the LH surge, and 58–68 days (63 expected) from the breeding date. Cats: 65 days from mating, range 63–67. Timeline events are typical, not guaranteed.
Breed data
Typical adult weight and lifespan for each breed are broad ranges based on breed standards and kennel-club breed pages. Individual dogs vary, and mixed breeds may fall anywhere in the range.
These calculators give estimates for information only. They are not veterinary advice. For health, feeding or breeding decisions, ask your vet.