Methodology

Last updated: 2026-05-13

Every Goodboy Atlas calculator uses a published formula traceable to a peer-reviewed source, a veterinary association guideline, or a regulatory dataset. This page lists each calculator, the formula, and the source. If you find an error or a more current source, tell us.

Age & growth

Dog age calculator

Primary method (AKC size-based): Year 1 = 15 human years; Year 2 = +9; Year 3+ = +4 (small), +5 (medium), +6 (large), +7 (giant).
Secondary method (Wang epigenetic-clock, 2020): human age = 16 × ln(dog age) + 31. Derived from Labrador Retriever DNA methylation; valid for adults only.
Sources: AKC "How to Calculate Dog Years to Human Years." Wang T, Ma J, Hogan AN, et al., "Quantitative Translation of Dog-to-Human Aging," Cell Systems (2020).

Cat age calculator

Method (AAFP Feline Life Stage): Year 1 = 15; Year 2 = +9; Year 3+ = +4 per year. Lifestyle adjustment for indoor vs outdoor expected lifespan.
Sources: AAFP-AAHA Feline Life Stage Guidelines (2021).

Puppy growth calculator

Method: Percent-of-adult-weight curves by size band, with linear interpolation between published control points (AAHA + Royal Canin).
Sources: AAHA Canine Life Stage Guidelines (2019); Hawthorne AJ et al., "Body-weight changes during growth in puppies of different breeds," J Nutr (2004); Royal Canin growth standards.

Calorie & weight

Daily calorie needs (dogs)

Method (RER × MER): RER (kcal/day) = 70 × W(kg)0.75. MER = RER × life-stage multiplier (puppy 2.0–3.0, adult intact 1.8, adult neutered 1.6, senior 1.4, geriatric 1.2). Activity adjustments −0.2 to +1.5. Weight-loss plan = 1.0 × RER for target weight.
Sources: National Research Council, Nutrient Requirements of Dogs and Cats (2006); WSAVA Global Nutrition Committee.

Daily calorie needs (cats)

Method: Same RER formula; cat-specific multipliers (adult intact 1.4, adult neutered 1.2 — lower than dogs). Weight-loss plan = 0.8 × RER for target weight (conservative for hepatic-lipidosis risk).
Sources: NRC 2006; AAFP-AAHA Feline Life Stage Guidelines (2021).

Calorie deficit (weight loss)

Method: Target kcal = ideal-weight MER × 0.8 (dogs) or 0.85 (cats). Weekly weight loss target 1–2% body weight (dogs), 0.5–1% (cats).
Sources: AAHA Weight Management Guidelines (2014, reaffirmed 2021).

Ideal weight

Method: ideal_weight = current_weight × (5 / BCS) where BCS uses the WSAVA 1–9 scale and 5 is the ideal point.
Sources: WSAVA Body Condition Score guidelines.

Food amount

Wet vs dry food split

Method: Daily kcal × wet fraction ÷ wet food density (kcal/g) = wet grams/day. Same for dry.
Sources: Manufacturer label disclosures (per AAFCO requirements).

Raw food (PMR / BARF)

Method: Adult dogs: 2–3% of body weight per day, split 80% muscle meat / 10% bone / 10% organs (5% liver + 5% other). Puppies: 5–10% depending on age.
Sources: Prey Model Raw (PMR) framework; Billinghurst I., Give Your Dog a Bone (BARF model basis); FEDIAF "Nutritional Guidelines for Complete and Complementary Pet Food" (2024).

Treat allowance

Method: 10% of daily kcal, regardless of species or life stage (AAHA "10% rule").
Sources: AAHA Weight Management Guidelines (2014, reaffirmed 2021).

Hydration

Water intake

Method: 1 mL water per kcal of MER (baseline). Environment multipliers compound: hot climate ×1.25, working dog ×1.4, lactating ×2.0. Water-from-food subtracted based on diet moisture content.
Sources: NRC 2006; AAHA Nutritional Assessment Guidelines.

Toxicity

Chocolate toxicity (dogs)

Method: Methylxanthine dose (theobromine + caffeine, mg/kg). Bands: <20 none, 20–40 mild, 40–60 moderate, 60–100 severe, >100 critical. Theobromine content per chocolate type from ASPCA + Pet Poison Helpline references.
Sources: ASPCA Animal Poison Control Center; Pet Poison Helpline; Merck Veterinary Manual.

Home & cost

Crate size

Method: Standard manufacturer size bands by weight. Refined by measurement: length = nose-to-tail + 4″, height = sitting head-top + 4″.
Sources: AKC Crate Sizing Guide; Midwest Homes for Pets sizing chart.

Lifetime cost of ownership

Method: Per-category annual cost tables (food, vet, grooming, supplies, insurance) by species / weight / coat / spending tier × expected lifespan, with year-1 setup adjustment and senior-year multiplier.
Sources: ASPCA Pet Care Costs (annual); AVMA U.S. Pet Ownership Demographics; Synchrony Financial Lifetime of Care Study (2024); NAPHIA premium data.

Cat litter cost & box count

Method: Litter usage ≈ 5 lb per cat per week (clumping clay average); cost = usage × per-pound retail price. Box count follows the "n + 1" rule (one box per cat plus one extra).
Sources: AAFP Feline Environmental Needs Guidelines (2013); Carney HC et al., "AAFP and ISFM Guidelines for Diagnosing and Solving House-Soiling Behavior in Cats," J Feline Med Surg (2014).

Comparison tools

Compare a dog and a cat

Method: Run each species through its own age formula above, then surface the human-equivalent ages side by side with life-stage labels.

Compare two dogs

Method: Two parallel AKC size-based age calculations, surfaced side by side with delta + plain-English summary.

Where we won't go

Drug dosing, diagnostic flowcharts, behavioural assessments via questionnaire, and breed-from-photo identification are all out of scope. These are either veterinary-clinic territory or technically unreliable.

Spotted an error or a more current source? Tell us.