How We Calculate
Every number on this site comes from published veterinary nutrition references — the same ones used in clinic. This page documents the method completely so any result can be reproduced by hand.
The core formula
RER (Resting Energy Requirement) = 70 × (body weight in kg)0.75, in kcal/day. MER = RER × life-stage factor: weight loss 1.0 (at ideal weight), inactive/obesity-prone 1.2, senior lower-activity 1.4, neutered adult 1.6, intact adult 1.8, weight gain 1.8–2.0, active/working 2.0–3.5, puppy 3.0 under 4 months, tapering smoothly to 2.0 by 8 months, gestation (last third) 3.0, and lactation by litter size — 3.25 for 1–2 pups, 4.0 for 3–4 pups, 5.5 for 5 or more (the midpoints of the published 3.0–3.5, 4.0 and 5.0–6.0 bands).
Sources: AAHA Nutritional Assessment Guidelines (2021), the Pet Nutrition Alliance calorie calculator, the Merck Veterinary Manual, WSAVA Global Nutrition Guidelines, and NRC (2006) Nutrient Requirements of Dogs and Cats. Where sources differ slightly (inactive adult is listed 1.2–1.4 across them), we default to the conservative end and show the factor on every result.
Where the factors come from
The factors are not ours — they come from the same references. The AAHA 2021 Nutritional Assessment Guidelines and the Pet Nutrition Alliance calculator publish the life-stage factors this site uses: 1.0 for weight loss at target weight, 1.2 inactive, 1.4 senior, 1.6 neutered adult, 1.8 intact, 2.0–3.5 active/working, 3.0 for young puppies tapering to 2.0, and the gestation and lactation bands listed above. NRC (2006) underpins the energy model behind them. Where the references disagree, we say so on the page and default to the conservative end — and every result shows its factor, so any vet can see exactly which multiplier produced the number. The senior factor and the meal-frequency rules have their own guides: feeding a senior dog and feeding schedules by age.
FEDIAF vs AAFCO: same formula, different nutrient rules
The energy maths is the same on both sides of the Atlantic: RER = 70 × kg0.75 and the life-stage factors do not change between the US and Europe. What differs is the nutrient-profile rules — AAFCO in the US, FEDIAF in Europe — which set the minimum protein and fat a complete food must contain per 1,000 kcal. Both set the adult-maintenance protein minimum at 18% dry matter, so the nutrition calculator's AAFCO check works for a European label too. And wherever a food's label gives kcal per kg, the conversion is identical regardless of origin: kcal/100 g is kcal/kg ÷ 10.
How this site is reviewed
The formulas on this site were reviewed by an independent veterinary consultant — the same person who checks the factors and sources on this page. A named reviewer, with credentials, will be published here once confirmed; until then, every factor and source is documented on this page so the work can be checked without taking our word for it. No author name is invented and no review is claimed that did not happen. If a factor or source on this page is wrong, the contact page is the fastest route — corrections are credited and fixed fast.
Converting calories to food
Grams = food kcal ÷ (food kcal per 100 g ÷ 100). Food kcal = MER minus the treat allowance (default 10%, capped by guidance from the same references). Cups are derived using measured kibble densities and are always labelled approximate — volume is not a reliable unit for energy-dense dry food.
Raw feeding
Percentage-of-body-weight feeding: adults 2–3% of ideal weight daily (2.5% default), puppies 8–10% tapering to adult rates. BARF split 70/10/5/5/10 (muscle meat / raw edible bone / liver / other secreting organ / vegetables & fruit); PMR 80/10/5/5.
Known limits
Individual energy needs vary by up to ±50% from any formula (stated by the Pet Nutrition Alliance and Ohio State's veterinary nutrition service). Our results are starting portions: weigh the dog every 2 weeks, and adjust by ~10% until weight and body condition are stable. Nothing here diagnoses or treats disease; dogs with medical conditions, and pregnant or nursing dogs, need veterinarian-set plans.
The life-stage factors, in one table
| Life stage | MER factor |
|---|---|
| Weight loss (at target weight) | 1.0 |
| Inactive / obesity-prone | 1.2 |
| Senior, lower activity | 1.4 |
| Neutered adult | 1.6 |
| Intact adult | 1.8 |
| Weight gain | 1.8–2.0 |
| Active / working | 2.0–3.5 |
| Puppy, under 4 months | 3.0 |
| Puppy, 4–8 months | taper 3.0 → 2.0 |
| Puppy, 8–12 months | 2.0 |
| Gestation (last third) | 3.0 |
| Lactation, 1–2 pups | 3.25 |
| Lactation, 3–4 pups | 4.0 |
| Lactation, 5+ pups | 5.5 |
Worked example: a 20 kg neutered adult
| Step | Value |
|---|---|
| RER = 70 × 200.75 | 662 kcal |
| MER = 662 × 1.6 | 1,059 kcal |
| Treat allowance (10%) | −106 kcal |
| Food energy | 953 kcal |
| Portion at 370 kcal/100 g | 258 g/day |
| Per meal (2 meals) | 129 g |
Tables are generated, not typed
Every chart on this site is computed by the same code as the interactive calculators, so the tables can never drift out of sync with the tools. Spot-check us: a 20 kg neutered adult gives RER 662, MER 1,059 kcal, and 258 g/day of a 370 kcal/100 g kibble after a 10% treat allowance.
Charts vs calculators: the bag chart and this calculator disagree for most pet dogs — see the head-to-head comparison of the two methods.
Last updated: 7 November 2026
Site questions
Is this site really free?
Yes — every calculator, table and breed page is free, with no sign-up and no email gate. The site costs little to run; if advertising or affiliate links ever appear, they will be labelled and will never change a calculation.
Who maintains the calculators?
One independent publisher with veterinary-consultant review of the formulas. Brand input is limited to published energy density; no manufacturer reviews or approves any page before it ships.
Where do the numbers come from?
The formulas and factors come from AAHA, the Pet Nutrition Alliance, the Merck Veterinary Manual, WSAVA and FEDIAF — detailed, with worked examples, on the method page linked from every footer.
I found an error — what happens next?
Write via the contact page with the page, your inputs and what you expected. Reproducible errors are fixed first, across every affected page, with the change dated on the method page.
Two worked checks anchor the method. A 20 kg neutered adult: RER = 70 × 20^0.75 = 662 kcal; MER at the 1.6 neutered factor = 1,059 kcal; on 370 kcal/100 g kibble with a 10% treat allowance removed, that is 258 g/day — the same figures published feeding references produce for this dog. A 5 kg puppy under four months runs at ×3.0 on the same RER base: 234 × 3.0 = 703 kcal. Every table on this site is regenerated from the formulas on this page whenever a factor changes, so the worked examples and the tables cannot quietly drift apart.
Sources, and what each one contributes: the AAHA nutritional assessment guidelines set the body-condition framework; the Pet Nutrition Alliance publishes the calorie calculator methodology clinics use; the Merck Veterinary Manual is the reference for energy requirements by life stage; WSAVA's global nutrition guidelines define how a food should be evaluated beyond its label; FEDIAF's nutritional guidelines are the European standard the locale method pages cite. When sources disagree, the method follows the clinic-facing one (Merck/PNA) and notes the difference rather than averaging silently.