Pet Calorie & Ideal Weight Calculator
How many calories does your dog or cat actually need each day? Enter your pet's weight, pick the species and life stage, and this calculator applies the standard veterinary RER and MER formulas to give you a daily calorie target, plus ideal weight guidance based on body condition score.
This is a starting estimate, not a prescription. Watch your pet's weight over 2–4 weeks and adjust portions up or down by about 10%. Always confirm with your veterinarian, especially for weight-loss plans, puppies, kittens, or pets with health conditions.
How to Use This Calculator
- Choose Dog or Cat.
- Enter your pet's current weight in kilograms or pounds.
- Pick the life stage that fits best. Neutered or spayed adults burn fewer calories than intact adults, and puppies and kittens need far more energy per kilogram.
- Select a body condition score. Run your hands along the ribs: if you can feel them with light pressure and see a waist from above, that is around a 5 (ideal).
- Press Calculate Calories to see the resting energy requirement (RER), the daily maintenance target (MER), and an estimated ideal weight.
How the Math Works
The calculator uses the same two formulas veterinarians use. First, the Resting Energy Requirement: RER = 70 × (body weight in kg)0.75. That is the energy a pet burns at rest in a comfortable environment. Then the RER is multiplied by a life-stage factor to get the Maintenance Energy Requirement (MER), the realistic daily calorie target:
| Life stage | MER factor |
|---|---|
| Puppy under 4 months | RER × 3.0 |
| Puppy 4–12 months | RER × 2.0 |
| Kitten | RER × 2.5 |
| Neutered / spayed adult | RER × 1.6 |
| Intact adult | RER × 1.8 |
| Senior | RER × 1.4 |
| Weight loss | RER × 1.0 |
Example: a 20 kg neutered adult dog has an RER of 70 × 200.75 ≈ 662 kcal, so the daily target is 662 × 1.6 ≈ 1,059 kcal. For ideal weight, each body condition point above 5 corresponds to roughly 10% excess body weight, so the tool divides the current weight by 1 + 0.10 × (BCS − 5) to estimate where your pet should land.
Tips for Feeding the Right Amount
- Read the kcal on the bag. Pet food labels list kcal per cup or per can, so divide your pet's daily target by that number to get portions.
- Count treats. Treats should stay under 10% of daily calories; the rest should come from complete food.
- Weigh food with a kitchen scale. Scoops routinely over-pour by 20% or more.
- Re-check monthly. As weight changes, the calorie target changes too, so recalculate after any noticeable gain or loss.
Frequently Asked Questions
What are RER and MER?
RER (Resting Energy Requirement) is the energy your pet burns at rest, calculated as 70 times body weight in kilograms raised to the power of 0.75. MER (Maintenance Energy Requirement) multiplies RER by a life-stage factor, such as 1.6 for a neutered adult or 3.0 for a young puppy, to give a realistic daily calorie target.
How accurate is this calorie calculator?
It uses the standard veterinary starting formulas, but individual pets can vary by 20% or more depending on breed, activity, and metabolism. Treat the result as a starting point, monitor body weight for a few weeks, and adjust portions by about 10% at a time.
How do I turn the calorie number into food portions?
Check the kcal per cup or per can printed on your pet food label, then divide the daily calorie target by that number. For example, a 1,000 kcal target with food at 400 kcal per cup means about 2.5 cups per day, split across meals.
What is a body condition score (BCS)?
BCS is a 1-to-9 hands-on scale vets use to judge whether a pet is underweight or overweight. A score of 4 to 5 is ideal: ribs are easy to feel but not see, and there is a visible waist. Each point above 5 represents roughly 10% extra body weight.
My pet needs to lose weight. Which number do I feed?
Select the "Weight loss" life stage, which feeds RER with no multiplier, and ideally enter the estimated ideal weight rather than the current weight. Weight-loss plans should always be supervised by a veterinarian, especially for cats, since rapid loss can be dangerous.