Sources & method

This site is run anonymously, so trust has to come from the method, not a face. Here is exactly where each number comes from — you can open every source and check it yourself.

How the numbers stay right

• Breed weights — 181 dog breeds and 11 cat breeds — come from two published sources, and every breed page names the one it used. 121 dog breeds lead with the American Kennel Club’s official standard — it is what American owners check against — and 60 with Wikidata’s open (CC0) breed data, published by the Wikimedia Foundation. All 11 cat breeds come from Wikidata: the AKC registers dogs only. A robot never writes a number — an automated check re-reads both sources every week and fails loudly if any figure has drifted. A human then reads the source and updates it by hand.
• When the two weight sources disagree, both are shown. They are not measuring the same thing: the AKC publishes a breed standard — separately for males and females — describing what a dog of that breed should weigh, while Wikidata aggregates published measurements. So a Great Dane reads 110–175 lb as a standard and rather wider as a measurement, and neither number is wrong. Picking one silently would hide a real disagreement, so the breed page names the second figure underneath the first.
• Where the AKC publishes no range — “under 28 pounds”, “100 pounds or more”, or two separate size varieties — no number is stored at all and its sentence is quoted as written. Inventing the missing end of the range to make it fit a chart would be a number no source published.
• The dog-age formula is the peer-reviewed epigenetic model of Wang et al. (2020), not the “multiply by 7” myth. It is covered by a test that checks the formula against the values published in the paper.
• The cat-age table follows International Cat Care’s published conversion. The Cornell Feline Health Center publishes a different one — a gap of 3 human years that holds constant past a cat’s second birthday — so the calculator shows both instead of picking one.
• Growth timing — that larger dog breeds take longer to reach adult weight — is from Hawthorne et al. (2004). How much a kitten weighs at each age is from DiGangi et al. (2019), a study that stops at 20 weeks and is never extrapolated past that.
• Calorie needs, for both dogs and cats, start from the same Merck Veterinary Manual formula for resting energy requirement. The cat figure is checked against a table the WSAVA Global Nutrition Committee publishes using a different formula.

The documents

• Wikidata — dog breed mass (property P2067)

  Wikimedia Foundation — query run 2026-07-22, CC0 license

• Wikidata — cat breed mass (property P2067)

  Wikimedia Foundation — query run 2026-07-28, CC0 license

• Breed weights — official AKC breed standards

  American Kennel Club — breed pages, accessed 2026-07-29

• Breed life expectancy — AKC breed pages

  American Kennel Club — breed pages, accessed 2026-08-10

• Longevity of companion dog breeds: those at risk from early death — Supplementary Table S3

  McMillan et al., Scientific Reports (2024) — 14:531, 584,734 UK dogs — Kaplan-Meier median survival for 155 breeds

• Life tables of annual life expectancy and mortality for companion dogs in the United Kingdom

  Teng et al., Scientific Reports (2022) — 12:6415, VetCompass — 30,563 deaths

• Life tables of annual life expectancy and risk factors for mortality in cats in the UK

  Teng et al., Journal of Feline Medicine and Surgery (2024) — 26(5), VetCompass — 7,936 deaths

• Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome

  Wang et al., Cell Systems — 2020, vol. 11, no. 2, p. 176–185.e6 (DNA methylation in 104 Labradors)

• Body-Weight Changes during Growth in Puppies of Different Breeds

  Hawthorne et al., Journal of Nutrition — 2004, vol. 134, p. 2027S

• Obesity in Cats — overweight threshold and why ideal weight varies

  International Cat Care — updated 26 September 2025

• Cat Body Condition Score — the 9-point scale

  WSAVA Global Nutrition Committee — June 2025 (descriptive scale: publishes no weight and no percentage)

• Growth standard charts for monitoring bodyweight in dogs of different sizes

  Salt et al., PLoS ONE — 2017, vol. 12, no. 9, e0182064 (correction 2024: data availability only)

• Nutritional Guidelines for Complete and Complementary Pet Food for Cats and Dogs

  FEDIAF (European Pet Food Industry Federation) — 2025 edition (growth curves Table VII-8a, growth energy VII-8b and VII-10)

• Antihistamine Dosages for Integumentary Disease in Animals

  Merck Veterinary Manual — dosage table, accessed 2026-07-30

• Urticaria (Hives, Wheals) in Animals — antihistamine course and the feline caution

  Merck Veterinary Manual — accessed 2026-07-30

• BENADRYL — diphenhydramine hydrochloride tablet, film coated (25 mg, single active ingredient)

  DailyMed, U.S. National Library of Medicine — FDA product label, accessed 2026-07-30

• Effect of diphenhydramine and cetirizine on immediate and late-phase cutaneous allergic reactions in healthy dogs

  Papich et al., Veterinary Dermatology — randomized, double-blinded crossover study, 12 dogs (abstract, PMID 31899570)

• Approximate Gestation Periods — gestation length in the bitch and the queen

  Merck Veterinary Manual — “Approximate Gestation Periods” table, accessed 2026-07-30

• Dystocia in Small Animals

  Merck Veterinary Manual — “Diagnosis of Dystocia in Small Animals” section, accessed 2026-07-28

• Factors affecting gestation duration in the bitch

  Eilts et al., Theriogenology — 2005, vol. 64, no. 2, p. 242–251

• Nutritional Requirements of Small Animals — energy requirements of the dog and cat

  Merck Veterinary Manual — “Energy” section, accessed 2026-07-23

• Chocolate Toxicosis in Animals

  Merck Veterinary Manual — “Methylxanthine Content of Various Types of Chocolate” table and “Etiology” section, accessed 2026-07-28

• ASPCA Poison Control

  ASPCA — 24-hour emergency line, accessed 2026-07-28

• Cat pregnancy — how long pregnancy lasts in cats

  International Cat Care — accessed 2026-07-30 (golden-test source, not used to build the calculation)

• Estrous length, pregnancy rate, gestation and parturition lengths, litter size, and juvenile mortality in the domestic cat

  Root et al., Journal of the American Animal Hospital Association — 1995, vol. 31, no. 5, p. 429–433 (golden-test source, not used to build the calculation)

• How old is your cat? — life stage and human equivalent age

  International Cat Care (Cat Friendly Clinic) — accessed 2026-07-28

• The Special Needs of the Senior Cat — cat age in human years

  Cornell Feline Health Center, Cornell University — accessed 2026-07-28 (golden-test source, not used to build the calculation)

• Calorie Needs for an Average Healthy Adult Cat in Ideal Body Condition

  WSAVA Global Nutrition Committee — updated July 2020 (golden-test source, not used to build the calculation)

• Assessment of body weight for age determination in kittens

  DiGangi et al., Journal of Feline Medicine and Surgery — 2019 (tables 1 and 2, weight-for-age, male and female)

• Kitten Age & Weight Chart

  ASPCA Pro — 2023 (golden-test source, not used to build the calculation)