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Dog Food Calculator

Estimate how many calories your dog needs each day and how many cups of food that is, using the resting energy formula from the Merck Veterinary Manual.

Results

ItemValue

Daily calories by weight

WeightRERDaily calories at this life stage
A starting point only. The Merck Veterinary Manual notes that dogs of the same weight can need about 30% more or fewer calories. Use your dog’s ideal weight, watch body condition, and adjust with your veterinarian. Treats count toward daily calories. This is not veterinary advice.

Quick Answer

Resting energy (RER) = 70 × (weight in kg)^0.75. A 40 lb (18.1 kg) neutered adult dog has an RER of about 615 kcal and needs about 1.6 × RER = 985 kcal a day. With food at 380 kcal per cup, that is about 2.59 cups a day.

Last updated: 3 November 2026 ·How we calculate this: the Merck Veterinary Manual RER and MER formulas

Table of Contents

How This Dog Food Calculator Works

Enter your dog’s weight, choose its life stage, and enter the calories per cup printed on the food bag. The calculator finds the resting energy requirement (RER) with the formula from the Merck Veterinary Manual, multiplies it by the factor for your dog’s life stage to get the daily maintenance energy requirement (MER), and turns that into cups per day and per meal.

Quick explanation: calories, not cups, are what count.

  • RER: the energy needed at rest.
  • MER: RER × a factor for age and neuter status.
  • Cups: depend on how many calories the food packs in each cup.

How to Use the Dog Food Calculator

  1. Enter your dog’s weight, ideally its healthy target weight.
  2. Choose the life stage.
  3. Enter the calories per cup from the food bag.
  4. Enter meals per day.
  5. Press Calculate and read calories and cups.

Core Formulas

  • RER (kcal/day): 70 × (body weight in kg)0.75
  • MER: RER × life stage factor
  • Neutered adult: 1.6 × RER. Intact adult: 1.8 × RER
  • Puppy under 4 months: 3 × RER. Over 4 months: 2 × RER
  • Cups per day: MER ÷ kcal per cup

Key Terms

  • RER: resting energy requirement, the calories needed at rest.
  • MER: maintenance energy requirement, daily calories for normal activity.
  • kcal: a kilocalorie, the same as a food Calorie.
  • Body condition score: a scale vets use to judge if a dog is too thin or too heavy.
  • Intact: not spayed or neutered.

Worked Example

A 25 lb puppy, 6 months old, eats food with 400 kcal per cup.

  • Weight = 25 ÷ 2.205 = 11.3 kg, so RER = 70 × 11.30.75 ≈ 433 kcal
  • MER = 2 × 433 = 865 kcal a day
  • Food = 865 ÷ 400 ≈ 2.16 cups a day

Real-Life Examples

  • Switching foods: a richer food at 450 kcal per cup needs fewer cups than one at 350.
  • Small dogs: a 10 lb neutered dog needs about 348 kcal a day.
  • Large dogs: an 80 lb neutered dog needs about 1656 kcal a day.
  • Weight-prone dogs: the 1.4 × RER factor gives a lower starting point.

Calculator vs Feeding Chart on the Bag

  • Bag chart: a general guide by weight, often on the generous side.
  • This calculator: uses your dog’s life stage and the food’s calories.
  • Both: are starting points. Your dog’s body condition is the real guide.

Daily Calories for Neutered Adult Dogs

Source: Merck Veterinary Manual formulas. A starting point only.

WeightRERDaily caloriesCups at 380 kcal/cup
5 lb1292070.5
10 lb2183480.9
20 lb3665851.5
30 lb4967942.1
40 lb6159852.6
50 lb72711643.1
60 lb83413353.5
80 lb103516564.4
100 lb122319585.2

What Changes How Much a Dog Needs

  • Activity: working and very active dogs need more.
  • Neutering: neutered dogs often need fewer calories.
  • Age: growing puppies need more per pound, and older dogs often less.
  • Body condition: adjust if your dog gains or loses weight.

A simple check is to feel your dog’s ribs. You should be able to feel them easily under a thin layer of fat, and see a waist from above. If the ribs are hard to find, feed a little less; if they stick out, feed a little more, and recheck in two to four weeks.

Common Mistakes to Avoid

  • Using cups from another food. Calories per cup differ a lot between foods.
  • Using an overweight dog’s current weight. Ask your vet about target weight.
  • Forgetting treats. They add calories.
  • Guessing cup size. Use a real measuring cup, or weigh the food.
  • Never adjusting. Check weight and body shape every few weeks.

Frequently Asked Questions

Find daily calories with RER × life stage factor, then divide by the calories per cup of your food.

RER = 70 × (weight in kg)^0.75.

A neutered adult needs about 1164 kcal a day as a starting point.

On the food bag or can, often listed as kcal/cup.

Yes. Merck lists 3 × RER under 4 months and 2 × RER after.

For weight changes, ask your vet. Many plans use the ideal weight.

Many adult dogs eat twice a day, and puppies often more. Ask your vet.

Yes. Include them in the daily calories.

Bag charts are general. Your dog may need fewer calories.

It is a starting point. Merck notes needs can vary by about 30% between dogs of the same weight.

No. Cats use different factors.

Yes, especially for puppies, seniors, pregnant dogs or dogs with health conditions.

References & Sources

SourceUsed ForLink
Merck Veterinary Manual, Nutritional Requirements of Small Animals RER formula and maintenance energy factors for dogs. https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals