Methodology

Last updated: 2026-05-21

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.

Ibuprofen toxicity (dogs)

Method: Ingested dose in mg/kg from tablet strength and count. Bands: <50 none expected, 50–100 GI irritation, 100–175 acute kidney injury, 175–300 severe nephrotoxicity with GI haemorrhage, >300 critical. Mechanism is dual: COX-1 inhibition strips gastric mucosal protection, and renal afferent constriction reduces kidney perfusion.
Sources: ASPCA Animal Poison Control Center; Pet Poison Helpline; Merck Veterinary Manual.

Marijuana / THC toxicity (dogs)

Method: Estimated THC dose in mg/kg, separating edibles (concentrated, often with chocolate or xylitol as a second toxin) from plant material. Ataxia and urinary incontinence are the characteristic signs; the practical risk in edibles is frequently the co-ingestant.
Sources: ASPCA Animal Poison Control Center; Pet Poison Helpline; Merck Veterinary Manual.

Mushroom poisoning (dogs)

Method: Not a dose calculation — identification is unreliable in the field and the dangerous species are not distinguishable from safe ones by appearance. Treated as a triage guide keyed to time since ingestion, with amatoxin-containing species (Amanita) as the worst-case assumption until proven otherwise.
Sources: ASPCA Animal Poison Control Center; Pet Poison Helpline; Merck Veterinary Manual.

Xylitol toxicity (dogs)

Method: Dose in mg/kg. Hypoglycaemia risk from about 100 mg/kg; hepatic necrosis risk from about 500 mg/kg. Gum piece counts vary enormously by brand, which is the dominant source of uncertainty in any estimate.
Sources: ASPCA Animal Poison Control Center; Pet Poison Helpline; Merck Veterinary Manual.

Grape and raisin toxicity (dogs)

Method: Deliberately NOT a dose threshold. Tartaric acid is the identified toxic principle and individual sensitivity varies so widely that no safe dose has been established — any ingestion is treated as a hotline call. Raisins are the higher-risk form because they are concentrated.
Sources: ASPCA Animal Poison Control Center; Pet Poison Helpline; Merck Veterinary Manual.

Acetaminophen toxicity (cats)

Method: Dose in mg/kg. Toxicity begins around 10 mg/kg. Cats lack sufficient glucuronyl transferase to conjugate the NAPQI metabolite, which is why the feline threshold sits roughly an order of magnitude below the canine one.
Sources: ASPCA Animal Poison Control Center; Pet Poison Helpline; Merck Veterinary Manual.

Lily toxicity (cats)

Method: Not dose-based. True lilies (Lilium and Hemerocallis) cause acute kidney injury from any exposure including pollen and vase water, so the guide is a time-to-treatment protocol rather than a threshold calculation.
Sources: ASPCA Animal Poison Control Center; Pet Poison Helpline; Merck Veterinary Manual.

Essential-oil toxicity (cats)

Method: Exposure-route triage rather than a dose model — dermal, oral and diffuser exposures differ in risk. Cats are deficient in the glucuronidation pathway that metabolises phenolic compounds, which is why tea tree and related oils are disproportionately toxic to them.
Sources: ASPCA Animal Poison Control Center; Pet Poison Helpline; Merck Veterinary Manual.

Grape toxicity (cats)

Method: Same tartaric-acid mechanism as dogs, with less published feline case data. Any exposure warrants a call; the absence of a feline dose threshold reflects missing evidence, not established safety.
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. US-baseline sources; UK readers see PDSA Animal Wellbeing Reports + RCVS data, Australian readers see AVA + PetSure surveys, Canadian readers see CVMA + Petsecure reports — same methodology framework, different national publishers.

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, behavioral 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.