A dog's daily calories: the exact formula against the 30 x weight + 70 shortcut, 2 to 45 kg, two ways
Our own calculation, 8 November 2026 (UTC). Formulas from the MSD Veterinary Manual (Nutritional Requirements of Small Animals): RER = 70 x (body weight in kg)^0.75; the linear form 30 x (body weight in kg) + 70, which MSD restricts to animals over 2 kg and under 45 kg; maintenance for healthy adult dogs 1.8 x RER intact, 1.6 x RER neutered, 1.4 x RER obesity-prone. Way 1: the power directly. Way 2: exp(ln 70 + 0.75 ln weight). The two agree to the last digit; the 10 kg result also matches Ohio State's worked example of about 400 Calories a day.
What we found
- The resting energy requirement (RER) of a dog is 70 x (body weight in kg)^0.75 kcal a day; for a 10 kg dog that is 393.6 kcal, which Ohio State's veterinary nutrition service rounds to about 400.
- The shortcut 30 x (weight in kg) + 70 gives 370 kcal for the same 10 kg dog, 6.0% less.
- The MSD Veterinary Manual allows the shortcut only for animals over 2 kg and under 45 kg. Inside that range it is within 2.5% from 15 to 20 kg, -6.0% at 5 kg and 10 kg, +8.1% at 30 kg and +16.8% at 45 kg.
- A neutered healthy adult dog needs about 1.6 x RER a day (MSD): 630 kcal at 10 kg, 1059 at 20 kg, 1436 at 30 kg and 1946 at 45 kg.
- At 45 kg, using the shortcut for a neutered adult gives 2272 kcal against 1946: 326 kcal a day more.
- The MSD multipliers for adult dogs are 1.8 x RER intact, 1.6 x RER neutered and 1.4 x RER for an obesity-prone dog; puppies get 3 x RER up to 4 months and 2 x RER after.
- A dog 10 times as heavy needs about 5.62 times the resting energy, not 10 times, because the requirement grows with weight to the 0.75 power (10^0.75 = 5.62).
| Weight | RER, exact (kcal/day) | Shortcut 30 x kg + 70 | Shortcut vs exact | Neutered adult, 1.6 x exact | 1.6 x shortcut |
|---|---|---|---|---|---|
| 2 kg | 117.7 | 130 | +10.4 % | 188 | 208 |
| 3 kg | 159.6 | 160 | +0.3 % | 255 | 256 |
| 5 kg | 234.1 | 220 | -6.0 % | 374 | 352 |
| 10 kg | 393.6 | 370 | -6.0 % | 630 | 592 |
| 15 kg | 533.5 | 520 | -2.5 % | 854 | 832 |
| 20 kg | 662.0 | 670 | +1.2 % | 1059 | 1072 |
| 25 kg | 782.6 | 820 | +4.8 % | 1252 | 1312 |
| 30 kg | 897.3 | 970 | +8.1 % | 1436 | 1552 |
| 35 kg | 1007.3 | 1120 | +11.2 % | 1612 | 1792 |
| 40 kg | 1113.4 | 1270 | +14.1 % | 1781 | 2032 |
| 45 kg | 1216.2 | 1420 | +16.8 % | 1946 | 2272 |
What this cannot tell you: your dog's activity, breed or body condition, the calories in your food (on the bag, per cup or per can), or what a vet would set for a dog that is losing or gaining weight.