Pet Calorie Needs Calculator

What this calculator does

Find out roughly how many calories your dog or cat needs each day. Feeding guides on pet food bags use one table for a wide range of animals. So they're often a poor fit for your own pet. Veterinarians start from a pet's resting energy requirement (RER), the calories it burns while resting. They multiply it by a life stage factor. That factor allows for growth, activity and whether the animal is spayed or neutered. This calculator does that estimate for you.

The RER is 70 × (body weight in kilograms)^0.75 kilocalories a day. The ^0.75 means "raised to the power 0.75", and a kilocalorie is the same as a food Calorie. The life stage factors come from the 2021 Nutrition and Weight Management Guidelines for Dogs and Cats. These were published by the American Animal Hospital Association (AAHA). Most factors are ranges, so the result is a range too. Treat it as a starting point to discuss with your veterinarian. Then adjust it as you watch your pet's weight and body condition.

Where it's used

Why this math matters outside the classroom:

• Dog feeding. An owner of a 10 kg neutered dog finds RER = 70 × 10^0.75 ≈ 394 kcal and plans about 550–630 kcal a day.
• Fractional exponents. Students evaluate 16^0.75 as the fourth root of 16 cubed, which is 2³ = 8, so a 16 kg dog's RER is 560 kcal.
• Puppy growth. A breeder feeds a 3 kg puppy under 4 months about 3 × 70 × 3^0.75 ≈ 479 kcal a day, split into several meals.
• Cat weight loss. For a cat with a 5 kg target weight, 0.8 × 70 × 5^0.75 gives a starting goal of about 187 kcal a day.
• Shelter care. Shelter staff estimate daily calories for each new arrival and convert them into cups of the shelter's food.

How to use it

1. Choose dog or cat, and enter the body weight in pounds or kilograms.
2. Choose the life stage and activity level that fits best.
3. If you like, enter the calories per cup from your pet food's label to get cups per day.
4. Feed toward the result and weigh your pet every few weeks. Adjust with your veterinarian.

What the inputs mean

Body weight

Use the current weight for a pet at a healthy weight. For weight loss, use the target weight your veterinarian sets, not the current weight. That's the weight the factor is meant for.

Life stage and activity

Spayed and neutered adults usually need less than intact ones. Puppies under 4 months grow fastest and need about three times their RER. Pregnancy, nursing and heavy work need individual veterinary advice and aren't included.

Food calories per cup (optional)

Pet food labels in the US list calories as kcal per kg and kcal per cup or can. Use the per-cup figure with a standard 8 fl oz measuring cup.

Formula and method

RER (kcal/day) = 70 × (body weight in kg)^0.75
daily calories = RER × life stage factor
dog factors: neutered adult 1.4–1.6, intact 1.6–1.8, inactive 1.0–1.2, weight loss 1.0, puppy under 4 months 3.0, 4 months to adult 2.0, light work 1.6–2.0, moderate work 2.0–5.0
cat factors: neutered adult 1.2–1.4, intact 1.4–1.6, inactive 1.0, weight loss 0.8, kitten 2.5
cups per day = daily calories ÷ kcal per cup; 1 lb = 0.45359237 kg

RER is the resting energy requirement in kcal (kilocalories, the same as food Calories) per day. The life stage factor is the multiplier for your pet's age and activity. Kcal per cup comes from your food's label.

Raising the weight to the power 0.75 reflects how energy use grows with body size. Bigger animals burn fewer calories per pound. A 40 kg dog weighs ten times as much as a 4 kg cat, but burns only about 5.6 times the resting calories. Multiplying by 70 gives kilocalories per day.

The life stage factor then scales the resting figure up for daily life. A neutered adult dog at a factor of 1.4–1.6 needs 40–60% more than its RER. A puppy under 4 months needs three times its RER to fuel growth. For weight loss, the factor is 1.0 for dogs or 0.8 for cats, applied at the target weight. That creates a gentle calorie deficit (fewer calories in than out).

Worked example

A 25 lb spayed adult dog.

1. Weight in kg: 25 × 0.45359237 = 11.34 kg.
2. 11.34^0.75 = 6.18, so RER = 70 × 6.18 = 432.6 kcal/day.
3. Daily calories: 432.6 × 1.4 = 605.6 to 432.6 × 1.6 = 692.1 kcal/day.
4. With a food of 350 kcal per cup: about 1.73 to 1.98 cups a day.

Result: Start at about 606–692 kcal/day (roughly 1.7 to 2 cups of a 350 kcal/cup food). Then adjust with your veterinarian.

Understanding the result

Start near the middle of the range and watch the scale. If an adult pet gains weight over a month, move toward the low end. If it loses weight it doesn't need to lose, move up.

The calories include treats and chews. Many veterinarians suggest keeping treats to a small share of the day's total, and cutting the main meals to match.

Assumptions and limitations

• The weight entered is the pet's current healthy weight, or the target weight for weight loss.
• The pet is healthy. The factors are general guidelines for typical animals.
• Calories per cup are as printed on the food label.
• It's an estimate, not a diagnosis or a feeding prescription. Individual needs can differ by 20% or more. Ask your veterinarian before changing your pet's diet.
• Pregnancy, nursing, heavy work, illness and recovery need individual veterinary advice and aren't covered.
• Less active or indoor pets may need less than the factors suggest, and very old pets' needs vary.

Frequently asked questions

Sources

• AAHA 2021 Nutrition and Weight Management Guidelines for Dogs and Cats: Energy Requirement Calculations (checked 2026-10-19)

How this calculator is checked

Method: RER = 70 × BW(kg)^0.75 and MER = RER × life stage factor, with feline and canine life stage factor ranges from the AAHA 2021 Nutrition and Weight Management Guidelines for Dogs and Cats (Energy Requirement Calculations table). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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