ðŸ§Ū Nutrition Science

The Complete Pet Calorie Guide

The exact veterinary formula behind MyPetDex's Calorie Calculator — how it works, worked examples, and where the numbers come from.

Try the Calculator →

The RER & MER Formula

MyPetDex doesn't guess at portions. Every recommendation starts from Resting Energy Requirement (RER) — the calories your pet's body burns at complete rest — then adjusts for how active they are and what life stage they're in.

RER = 70 × (body weight in kg)0.75 The 0.75 exponent accounts for metabolic scaling — smaller pets burn more calories per pound than larger ones.

From there, we calculate Maintenance Energy Requirement (MER) — the number that actually tells you how much to feed:

MER = RER × Life Stage & Activity Factor × Body Condition Adjustment Spayed/neutered pets get a slightly lower factor than intact pets at the same activity level, since fixed pets typically have a slower metabolism.

See the Math in Action

Three real scenarios, calculated step by step using the exact same lookup table as the calculator on our homepage.

This is a starting point. Adjust with your vet to keep your pet at a healthy weight.

🐕 Adult dog, 25 lb, moderate activity, neutered

Weight25 lb → 11.3 kg
RER≈ 433 kcal
Life stage & activity ×1.6
BCS (ideal) ×1.0
≈ 693 kcal/dayMaintenance Energy Requirement

ðŸū Puppy, 15 lb, 6 months (4+ months)

Weight15 lb → 6.8 kg
RER≈ 295 kcal
Puppy factor ×2.0 (4+ months)
BCS (ideal) ×1.0
≈ 590 kcal/dayMaintenance Energy Requirement

ðŸĶī Senior dog, 50 lb, neutered

Weight50 lb → 22.7 kg
RER≈ 727 kcal
Senior factor ×1.2
BCS (6, mildly over) ×0.9
Final factor (floor 1.0) ×1.08
≈ 786 kcal/dayMaintenance Energy Requirement

The Exact Table Our Calculator Uses

This is the single biggest factor pet owners get wrong — and it changes depending on whether your pet is spayed/neutered or intact.

Dogs and cats use separate tables (neutered / intact). Same factors as the MyPetDex app.

Dogs — Puppy ×3.0 under 4 months / ×2.0 from 4 months

Based on age, not weight. Growing bodies need significantly more energy regardless of how active they seem.

Dogs — Adult Low (indoor) ×1.2 / ×1.4

Brief bathroom-break walks only, rests most of the day.

Dogs — Adult Moderate ×1.6 / ×1.8

30–60 minutes of walking or play daily — fits most household pets.

Dogs — Adult High (sport) ×1.8 / ×2.0

1–2+ hours of daily exercise — hiking, running, swimming, working/sporting dogs.

Dogs — Senior ×1.2 / ×1.4

Metabolism slows with age, but protein needs stay high. Senior-formulated food with joint support is worth considering.

Cats — Kitten ×2.5

One factor for growing kittens (under or over 4 months).

Cats — Adult Low ×1.0 / ×1.0

Mostly indoor, low activity.

Cats — Adult Moderate ×1.2 / ×1.4

Typical household cat with regular play.

Cats — Adult High ×1.4 / ×1.6

Very active outdoor or high-play cats.

Cats — Senior ×1.2 / ×1.4

Slightly lower energy needs with age.

Pregnant (dogs & cats) ×2.0

Energy needs rise sharply, especially in the final third of pregnancy.

Nursing (dogs & cats) ×3.0

The highest energy demand of any life stage — nursing mothers may need to eat multiple times their normal maintenance amount.

Fine-Tuning for Your Pet's Actual Body

The life-stage factor gets a final nudge based on where your pet sits on the 9-point Body Condition Score (BCS) scale — pulling the target up for underweight pets and down for overweight ones. After BCS is applied, the final factor is never below 1.0 for dogs or 0.8 for cats.

1–2 — Very thin / thin ×1.3 / ×1.2

Portions increased to help rebuild healthy weight.

3–4 — Underweight / lean ×1.1 / ×1.05

A small boost above baseline maintenance.

5 — Ideal ×1.0

No adjustment — this is the target most pets should be maintained at.

6–7 — Overweight ×0.9 / ×0.8

Portions reduced to bring weight back down gradually.

8–9 — Obese / severely obese ×0.7 / ×0.6

A significant reduction — pair with your vet's guidance for a safe weight-loss plan.

The Calculator Is a Starting Point

This is a starting point. Adjust with your vet to keep your pet at a healthy weight. Every pet's metabolism is a little different — recheck body condition every 2–4 weeks and adjust from there.

Ideal condition: Ribs easily felt but not visible, a visible waist from above, and an abdominal tuck from the side.
Gaining weight? Reduce daily portions by 10–15%.
Losing weight? Increase daily portions by 10–15%.
Sudden or dramatic changes? Talk to your vet — it could signal a health issue, not just a feeding one.
⚠ïļ Important: This calculator provides an estimate only and does not replace professional veterinary advice. Always confirm feeding plans with your vet, especially for pets with health conditions.

Built on Published Standards

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AAFCO 2023

The official U.S. nutrient profile standard for pet food, covering every life stage.

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USDA FoodData Central

400,000+ ingredient entries from the U.S. government's public nutrition database.

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Veterinary Nutrition References

Calorie targets use the standard resting energy formula used in veterinary nutrition, with published life-stage factors.

See our full data sources →

Common Questions

How accurate is this calculator?

It uses the standard resting energy formula used in veterinary nutrition, with published life-stage factors. It's a strong starting point, but every pet's metabolism varies — treat the result as a baseline to adjust from, not a fixed rule.

Should I adjust for my pet's breed?

Some breeds run leaner or heavier metabolisms than average (sighthounds vs. brachycephalic breeds, for example). Start with the calculated number, then adjust based on body condition over a few weeks.

How often should I feed my pet?

Most adult dogs and cats do well on 2 meals a day. Puppies and kittens typically need 3–4 smaller meals to support growth and blood sugar stability.

Do treats count toward the daily total?

Yes — treats should make up no more than about 10% of daily calories. Large or frequent treats can throw off the whole calculation.

Track it all in one place

Calorie targets, vaccine records, and reminders will live in the iPhone app when it launches.

Coming soon to the App Store