Method and sources
Each calculator on this site, the equation behind it, where that equation comes from and where it breaks down.
Resting and maintenance energy
RER = 70 × (body weight in kg) ^ 0.75
The allometric resting energy requirement used throughout veterinary nutrition. Maintenance energy requirement is RER multiplied by a life-stage factor: 1.6 neutered adult, 1.8 intact adult, 1.4 gain-prone, 1.0 during weight loss, 2.0 puppy from four months, 3.0 puppy under four months, and roughly 2.0–5.0 for genuinely working dogs, of which this site offers 2.5 as a representative value.
Limits. Individual requirement at a given weight varies by roughly ±20%. The formula is a starting ration to be corrected by monthly weighing, not a prescription. Source: WSAVA Global Nutrition Guidelines.
Body condition and target weight
On the nine-point body condition scale, 5 is ideal and each point above corresponds to
approximately 10% above ideal body weight, giving
ideal = current ÷ (1 + 0.1 × (score − 5)). Safe loss is conventionally 1–2%
of body weight per week, and the recommended starting ration for reduction is the resting
energy requirement of the target weight.
Limits. Scoring is subjective and coat length interferes with it badly; have a vet or vet nurse confirm the score. Source: WSAVA Global Nutrition Guidelines.
Human-equivalent age
human equivalent = 16 × ln(dog age in years) + 31
From the 2020 comparison of DNA methylation in dogs and humans.
Limits. The curve was fitted to Labrador Retrievers and does not adjust for size, though size strongly affects canine ageing. It is not defined below one year, and this site declines to extrapolate there. Source: Wang et al., Cell Systems 2020.
Water intake
Approximately 50–60 ml per kg per day for a healthy adult at rest.
Limits. This is a rule of thumb rather than a measured constant, which is why it is presented as a range. Food moisture, heat, activity, lactation and several medications all shift it substantially. Its value is in establishing an individual baseline, not in comparing a dog against a population.
Puppy growth projection
Adult weight is projected by dividing current weight by the share of adult weight typically reached at that age for that adult size class, interpolated between reference points.
Limits — read this one. Unlike the formulae above, these growth shares are approximations synthesised from conventional guidance, not values from a single published dataset. They are the weakest numbers on this site. Output is therefore given as a ±15% range, and on breed pages it is additionally checked against that breed's published adult range so that an implausible projection is flagged rather than reported as fact.
Breed reference figures
Weight and height ranges are extracted programmatically from English Wikipedia breed infoboxes. Each breed page records the revision identifier the figures were taken from. Two categories are excluded rather than published: breeds whose article gives no usable weight range, and breeds whose article merges several size varieties into a single span too wide to describe an individual animal. Wikipedia text is used under CC BY-SA 4.0; the underlying measurements are facts and are attributed as a matter of practice.
What is deliberately absent
No medication dosing calculators, no toxicity or "can my dog eat this" pages, and no diagnostic tools. The first can kill an animal through an arithmetic error compounded by breed-specific drug sensitivities; the second cannot be sourced to any authoritative dataset and would amount to publishing invented facts about animal safety.