How we work it out
Every figure comes from the Merck Veterinary Manual, the AAHA guidelines or AAFCO, read on 2026-11-07. Each result is a starting point to check with your pet’s veterinarian.
Energy factors
Maintenance energy is the resting energy times a factor. The two sources disagree on some rows; the calculators use Merck’s value and show the whole range.
| Status | Merck | AAHA 2021 |
|---|---|---|
| Neutered adult (dog / cat) | 1.6 / 1.2 | 1.4 to 1.6 / 1.2 to 1.4 |
| Intact adult (dog / cat) | 1.8 / 1.4 | 1.6 to 1.8 / 1.4 to 1.6 |
| Inactive or obesity prone (dog / cat) | 1.4 / 1.0 | 1.0 to 1.2 / 1.0 |
| Weight loss, on ideal weight (dog / cat) | not given | 1.0 / 0.8 |
| Puppy under 4 months | 3.0 | 3.0 |
| Puppy 4 months or older | 2.0 | 2.0 |
| Kitten | 2.5 | 2.5 |
Dog food and puppy feeding
Resting energy requirement RER = 70 × (weight in kg)^0.75 kcal a day, at any weight. Maintenance energy MER = RER × the factor of the status. Cups a day = MER ÷ kcal per cup; grams a day = MER ÷ (kcal per kg) × 1,000; cans a day = MER ÷ kcal per can. Treats are at most 10% of MER, so on a day with treats the food is 90% of the amount. The puppy page is the same engine started at a puppy’s weight.
Merck says any figure is a starting point and a dog may need 30% more or less. The exponent has no exact rational value, so RER is rounded to a millionth of a kilocalorie.
Hand-worked cases
- AAHA Box 1, a 10 lb dog taken as 4.5 kg: RER = 4.5^0.75 × 70 = 216 kcal a day. 216 kcal
- The same dog at AAHA’s low factor 1.4 for a neutered adult (AAHA rounds RER first and prints 302): 216.28 × 1.4. 303 kcal
- A neutered 10 kg dog: 10^0.75 = 5.6234, RER = 393.64, × 1.6 (Merck) = 629.82. 630 kcal
- The same dog on food of 360 kcal a cup: 629.82 ÷ 360. 1.75 cups
- The same dog on food of 3,600 kcal per kg: 629.82 ÷ 3,600 × 1,000. 174.95 g
- A puppy under 4 months of 10 kg, factor 3.0: 393.64 × 3. 1,181 kcal
Sources
- Merck Veterinary Manual, Nutritional Requirements of Small Animals (Sanderson, last updated September 2024), read 2026-11-07
- Merck Veterinary Manual, Daily maintenance energy requirements for dogs and cats, read 2026-11-07
- 2021 AAHA Nutrition and Weight Management Guidelines, Box 1, read 2026-11-07
- 2021 AAHA Nutrition and Weight Management Guidelines for Dogs and Cats (JAAHA 2021, PDF copy), read 2026-11-07
- AAFCO, Understanding Pet Food: Calories, read 2026-11-07
Cat food and kitten feeding
The same RER and treat rule as for dogs, with the cat factors. Cups of dry food = MER × (1 − wet share) ÷ kcal per cup; cans of wet food = MER × wet share ÷ kcal per can, the share being the part of the calories that comes from wet food. The kitten page is the same engine started at a kitten’s weight, factor 2.5.
Merck notes that kittens can alternatively be fed free choice.
Hand-worked cases
- A neutered 4 kg cat: 4^0.75 = 2.8284, RER = 197.99 kcal. 198 kcal
- The same cat, factor 1.2 (Merck): 197.99 × 1.2. 238 kcal
- Half the calories from wet food of 80 kcal a can: 237.59 × 0.5 ÷ 80. 1.48 cans
- The other half from dry food of 350 kcal a cup: 237.59 × 0.5 ÷ 350. 0.34 cups
Sources
- Merck Veterinary Manual, Nutritional Requirements of Small Animals (Sanderson, last updated September 2024), read 2026-11-07
- Merck Veterinary Manual, Daily maintenance energy requirements for dogs and cats, read 2026-11-07
- 2021 AAHA Nutrition and Weight Management Guidelines, Box 1, read 2026-11-07
- AAFCO, Understanding Pet Food: Calories, read 2026-11-07
Dog chocolate toxicity
Dose in mg/kg = grams eaten × milligrams of theobromine and caffeine per gram of that chocolate ÷ the dog’s weight in kg. Per gram: cocoa powder 28.5, unsweetened baking chocolate 15.5, cocoa bean hulls 9, semisweet and sweet dark chocolate 5.3 to 5.6 (the top is used), milk chocolate 2.3, white chocolate 0.04. Bands: mild signs from 20 mg/kg, heart effects from 40 to 50, seizures from 60. An ounce is 28.349523125 g.
Every result tells you to call a veterinarian or the ASPCA Animal Poison Control Center, however low the figure. Merck gives no figure between 50 and 60 mg/kg, so the heart-effects band runs from 40 to 60.
Hand-worked cases
- A 10 kg dog and 50 g of milk chocolate: 50 × 2.3 mg. 115 mg
- The same dog: 115 mg ÷ 10 kg, below the 20 mg/kg line and still a reason to call. 11.5 mg/kg
- Milk chocolate that reaches 20 mg/kg in a 10 kg dog: 200 mg ÷ 2.3 mg per gram. 87 g
Sources
Dog pregnancy due date
The window is the date you know plus 58 to 72 days from the first day the female allowed breeding, 64 to 66 days from the LH surge or the first rise of progesterone above 2 ng/mL, or 56 to 58 days from the first day of diestrus. The page gives the whole window, never one day.
A veterinarian can narrow the window with ovulation timing.
Hand-worked cases
- Breeding from 1 March 2026: 30 days to 31 March, 28 more, is day 58. Apr 28, 2026
- The same date, day 72: 30 days to 31 March, 30 to 30 April, 12 more. May 12, 2026
- An LH surge on 1 March 2026, day 64. May 4, 2026
Sources
Left out, and why
- NRC 2006 (Nutrient Requirements of Dogs and Cats). A paid book that the team has not read, so it is not cited until someone reads the actual table.
- Dog age in human years. The only formula verified (Wang et al., Cell Systems 2020) was fitted on 104 Labrador retrievers, and the AVMA size chart could not be read. A size-blind formula from one breed is not enough.
- Cat age in human years. The chart credited to AAHA and AAFP is not in the primary source that was found, which gives life stages only.
- Raw and homemade portions as a percentage of body weight. No veterinary primary source. The AVMA discourages raw or undercooked animal-source protein, and WSAVA says a homemade diet should be formulated by a board-certified veterinary nutritionist.
- Puppy adult-weight estimates. Every rule found online is unsourced; no published growth curve was found.
- Breed factors. Breed does not enter the Merck or AAHA formula; weight and status do. See the guide on dog food by breed.
- Pregnancy and lactation feeding. AAHA’s ranges (3.0 for the last 21 days of gestation, 3.0 to 6.0 or more in lactation) are too wide to give one number, so the pages send you to the veterinarian.
- Water intake, xylitol and grape thresholds. No primary threshold was verified.