RER (Resting Energy Requirement) = 70 × weight_kg^0.75. It's the kcal needed at complete rest. MER (Maintenance Energy Requirement) = RER × an activity/life-stage multiplier (1.0-3.0). Adult neutered dog: 1.6 × RER. Active intact: 1.8. Puppy < 4 mo: 3.0. Adult cat: 1.2-1.4. Active outdoor cat: 1.6.

How do I convert kcal to cups or grams?

Check your food bag for 'kcal/kg' or 'kcal/cup'. Typical adult dog dry: 350-450 kcal/cup. Adult cat dry: 350-450 kcal/cup. Wet food is much less calorie-dense (~30-40 kcal/oz). Divide your daily kcal by the food's density to get serving size.

Why does life stage matter so much?

Puppies and kittens grow rapidly — energy demand peaks around 3-4 months at 2.5-3.0× RER, then drops as growth slows. Pregnant or lactating animals need 2-4× RER (lactation peaks at week 4). Senior pets often drop to 1.0-1.2× RER as activity falls.

What about overweight pets?

For weight loss, use 1.0 × RER of TARGET (ideal) weight, not current weight. This produces a gentle deficit. Reassess monthly and adjust. Severe obesity may require veterinary supervision and prescription weight-loss food.

Are these numbers exact?

No — individual variation is ±20-30%. Two same-breed, same-weight dogs can need very different calories. Use this as a starting point, then adjust based on body condition score (BCS) over weeks. The pet's body, not the calculator, has the final word.

Should I follow the bag's feeding chart?

Bag charts often overestimate by 10-25% because manufacturers worry about under-feeding complaints. The RER × MER formula is more conservative and aligns with veterinary teaching hospital recommendations.

Dog & Cat Food Portion Calculator (RER / MER)

Pet Care· 5 tools

Free pet food portion calculator. Uses the veterinary-standard Resting Energy Requirement (RER = 70 × weight_kg^0.75) multiplied by life-stage and activity factors (MER multiplier) to produce daily kcal. Convert kcal to grams using your specific food's caloric density (printed on the bag, typically 350-450 kcal/cup for adult dog kibble).

Species

Weight

unit

Life stage / activity

Food kcal per cup

Check your bag. Typical adult dry: 350–450 kcal/cup. Wet: ~30–40 kcal/oz.

Formula · RER = 70 × kg^0.75 · MER = RER × multiplier

±20-30% individual variation · adjust based on body condition over weeks

Daily food

2.1 cups

~256 g (assumes ~120 g/cup dry kibble)

Daily kcal (MER)854

RER baseline534

Multiplier×1.6

Disclaimer: For informational purposes only. This is not veterinary advice — consult a qualified veterinarian for medical or dietary decisions about your pet.

Frequently Asked Questions

References

WSAVA Global Nutrition Guidelines — World Small Animal Veterinary Association

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