# How much dog food should I feed?

Estimates how many calories a dog needs a day (RER = 70 × kg^0.75 times a life-stage factor) and how many cups or grams of its food that is, per day and per meal.

- Page: https://www.acalculator.org/biology/dog-food-calculator
- JSON spec: https://www.acalculator.org/biology/dog-food-calculator.json
- Version: 70a13f9e383f

## Default answer

Example with the default inputs (Dog’s weight 22 lb, Life stage Adult, neutered (1.6), Calories per cup 350, Meals a day 2): A 22 lb dog needs about 629 kcal a day: 1.8 cups of this food, 0.9 cups per meal.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| w | Dog’s weight | The dog’s body weight now (for weight loss, its target weight). |
| stage | Life stage | The dog’s life stage, which sets the factor × RER. |
| k | Factor × RER | The factor your vet gives, for example 2 to 5 for working dogs. |
| cup | Calories per cup | The food’s kcal per 8 oz measuring cup, from the bag or can. |
| kg | Calories per kg (optional) | The food’s kcal per kilogram, from the label, to get grams; leave empty to skip. |
| meals | Meals a day | How many meals the daily amount is split into. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| mer | Calories a day | The daily energy requirement: the factor × RER. |
| cups | Cups a day | Calories a day ÷ calories per cup. |
| perMeal | Cups per meal | Cups a day ÷ meals a day. |
| grams | Grams a day | Calories a day ÷ calories per kilogram × 1,000, when calories per kg are typed. |
| rer | Resting energy (RER) | 70 × (weight in kg)^0.75: the calories a day at rest. |
| factorUsed | Factor used | The life-stage factor × RER. |

## Method

RER = 70 × (weight in kg)^0.75 kcal a day; calories a day = factor × RER; cups = calories ÷ kcal per cup; grams = calories ÷ kcal per kg × 1,000.

## Assumptions

- The factors are starting points for healthy dogs; a vet adjusts them to the dog’s body condition.
- Treats and table food are not counted: take their calories off the daily total.
- A cup is a standard 8 oz measuring cup, the one the label’s kcal per cup refers to.

## Worked examples

1. w = 30.45, stage = loss, cup = 350, meals = 2 gives rer = 907.378559, mer = 907.378559, cups = 2.59251, perMeal = 1.296255. Source: Today’s Veterinary Nurse, Nutrition Math 101 (Carlson, 2023): a 30.45 kg dog has RER = 70 × 30.45^0.75 = 907 kcal a day; weight loss uses 1.0 × RER, https://todaysveterinarynurse.com/nutrition/veterinary-nutrition-math/.
2. w = 10, stage = neutered, cup = 350, kg = 3,600, meals = 2 gives rer = 393.638928, mer = 629.822284, cups = 1.799492, grams = 174.950635. Source: Ohio State University Veterinary Medical Center, Companion Animal Nutrition Support Service: RER = 70 × kg^(3/4), about 400 Calories a day for a 10 kg dog, https://vmc.vet.osu.edu/services/companion-animal-nutrition-support-service; dogs: intact 1.8, neutered 1.6, obesity prone 1.4, puppies under 4 months 3, over 4 months 2 × RER, https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals.
3. w = 22.679619, stage = intact, cup = 400, meals = 2 gives rer = 727.48635, mer = 1,309.475429, cups = 3.273689. Source: Dogs: intact 1.8, neutered 1.6, obesity prone 1.4, puppies under 4 months 3, over 4 months 2 × RER, https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals.
4. w = 5, stage = puppy, cup = 420, meals = 4 gives mer = 702.17732, perMeal = 0.417963, factorUsed = 3. Source: Dogs: intact 1.8, neutered 1.6, obesity prone 1.4, puppies under 4 months 3, over 4 months 2 × RER, https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals.
5. w = 20, stage = custom, k = 4, cup = 500, meals = 2 gives mer = 2,648.076505, factorUsed = 4. Source: Dogs: intact 1.8, neutered 1.6, obesity prone 1.4, puppies under 4 months 3, over 4 months 2 × RER, https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals (factor set by the vet).

## FAQ

### How much should I feed my dog a day?

Work out its calories a day, then divide by the calories in a cup of its food. A 10 kg (22 lb) neutered adult needs about 70 × 10^0.75 × 1.6 = 630 kcal a day; with food at 350 kcal a cup that is 1.8 cups a day.

### What is RER?

The resting energy requirement: the calories a dog burns at rest. RER = 70 × (body weight in kg)^0.75. A 30.45 kg dog has an RER of about 907 kcal a day.

### What life-stage factor should I use?

The Merck Veterinary Manual gives 1.6 × RER for a neutered adult, 1.8 for an intact adult, 1.4 for an adult prone to gaining weight, 3 for a puppy under 4 months and 2 for a puppy from 4 months to adult. For weight loss, 1.0 × RER at the target weight is a common start. Working dogs need more; ask your vet.

### Where do I find the calories per cup?

On the food label. Most dog food labels give the calories as kcal per kilogram and kcal per cup or can. Type the kcal per kilogram as well to get grams, which is more exact than cups.

### Why does a big dog not need twice the food of a dog half its size?

Energy needs grow with weight to the power 0.75, not in step with weight. A 20 kg dog needs about 70 × 20^0.75 = 662 kcal at rest, only 1.68 times the 394 kcal of a 10 kg dog.

### Is this amount exact for my dog?

No. The Merck Veterinary Manual calls any such amount a starting point: dogs of the same weight can need more or less. Weigh your dog every few weeks and feed a little more or less to keep a healthy body condition; your vet can help.

## Sources

- Merck Veterinary Manual, Nutritional Requirements of Small Animals: RER = 70 × (body weight in kg)^0.75; daily energy for dogs: intact adult 1.8, neutered adult 1.6, obesity prone 1.4, puppies under 4 months 3, puppies over 4 months 2 × RER. Retrieved 2026-10-02. https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals
- Today’s Veterinary Nurse, Nutrition Math 101: Important Calculations for Dogs and Cats (E. Carlson, 2023): RER = 70 × BW^0.75; weight loss 1.0 × RER; a 30.45 kg dog has RER = 907 kcal a day. Retrieved 2026-10-02. https://todaysveterinarynurse.com/nutrition/veterinary-nutrition-math/
- The Ohio State University Veterinary Medical Center, Companion Animal Nutrition Support Service: RER = 70 × kg^(3/4); a 10 kg dog needs about 400 Calories a day. Retrieved 2026-10-02. https://vmc.vet.osu.edu/services/companion-animal-nutrition-support-service