Dog Food Portion Calculator
How much to feed a dog starts with how much energy it needs each day, and that follows a two-step calculation. This tool first works out the resting energy requirement, or RER, which is 70 multiplied by the dog's body weight in kilograms raised to the power 0.75, the exponent that describes how energy use scales with size. It then multiplies the RER by an activity factor that reflects how busy and what life stage the dog is, giving the estimated daily energy requirement in kilocalories. From there you divide by the calorie content on the food label to get a daily portion and split it across meals. Enter your own weight and activity factor to set a starting point for a new food, check whether a portion looks reasonable, or plan a gentle weight change with a lower factor. The exponent of 0.75 matters: energy use does not rise in proportion to weight, so a simple per-kilogram rule overfeeds big dogs. Treat the result as a starting estimate, watch your dog's body condition, and confirm with your veterinarian. Every figure here is computed deterministically from the standard RER formula, shown in full below, with a worked example that reconciles exactly to the calculator so you can follow each step.
Daily calories equal the resting energy requirement times an activity factor: kcal = (70 x kg^0.75) x factor. A 20 kg dog at an activity factor of 1.6 has an RER of 662.02 kcal and a daily need of about 1,059.23 kcal.
Daily calorie formula
RER = 70 x (weight in kg)^0.75
Daily energy = RER x activity factor
weight = body weight (kg)
factor = activity / life-stage multiplier
Daily energy = estimated daily need (kcal)
The resting energy requirement is the baseline calories at rest; multiplying by the activity factor scales it up to a typical day's energy need.
Worked example
A 20 kg adult dog with an activity factor of 1.6.
- 20^0.75 = 9.4574
- RER = 70 x 9.4574 = 662.02 kcal
- Daily energy = 662.02 x 1.6 = 1,059.23 kcal
The dog needs about 1,059.23 kcal a day. These are the calculator's default inputs, so the result above matches the widget exactly.
Resting energy requirement by weight
RER rises with body weight, but less than in direct proportion.
| Weight (kg) | RER (kcal) | At factor 1.6 (kcal) |
|---|---|---|
| 5 | 234.06 | 374.49 |
| 10 | 393.64 | 629.82 |
| 20 | 662.02 | 1,059.23 |
| 30 | 897.21 | 1,435.53 |
Pet food labelling and nutrition oversight: US Food and Drug Administration (FDA).
Dog food portion calculator: frequently asked questions
How are a dog's daily calories estimated?
Start with the resting energy requirement (RER), which is 70 multiplied by the dog's body weight in kilograms raised to the power 0.75. Then multiply the RER by an activity (or life-stage) factor that reflects how active the dog is. The result is the estimated daily energy requirement in kilocalories.
What activity factor should I use?
Typical factors run from about 1.2 for an inactive or weight-loss dog, up to 1.6 for a neutered adult at a normal activity level, and higher still for working dogs, puppies or pregnancy. This calculator defaults to 1.6. Choose the factor that matches your dog and confirm with your veterinarian.
How do I turn calories into a food amount?
Read the calorie content per cup or per gram on the food label (most US pet foods list kcal per cup), then divide the daily calorie target by that figure to get the daily portion. Split the total across the meals you feed each day.
Is this a substitute for veterinary advice?
No. The formula gives a starting estimate only. A dog's real needs depend on breed, age, health, body condition and metabolism. Monitor your dog's weight and body condition and adjust the amount, and ask your veterinarian for individual guidance.
Why is body weight raised to the power 0.75?
Energy use does not scale in direct proportion to body mass; it scales with a metabolic exponent close to 0.75, a relationship seen across many species. Using that exponent gives a far better estimate of resting energy than simply multiplying by weight.
Official sources
- Pet food labelling, safety and nutrition oversight: US Food and Drug Administration (FDA). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not veterinary, financial, tax, legal or investment advice.