Pet Food Portion Calculator
Last updated: 2026-06-25
The recommended daily food is found by taking the Resting Energy Requirement RER = 70 × weight (kg)^0.75, multiplying by an activity factor to get the Maintenance Energy Requirement MER, then dividing by the food's calories per kilogram to convert to grams.
The formula is daily food (g) = MER (kcal) ÷ food kcal/kg × 1000. (An estimate for reference only — adjust while watching weight changes.)
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Recommended daily food
0 g
| Item | Value |
|---|---|
| RER (Resting Energy Requirement) | |
| MER (Maintenance Energy Requirement) | |
| Food calories | |
| Recommended daily food |
The result is an estimate for reference only. The actual amount depends on body condition score (BCS), treats, and health status, so consult a veterinarian for an accurate diet.
How to use
- Enter weight — Enter your pet's current weight in kilograms.
- Select activity level — Choose the activity level (MER factor) that matches the pet's status — neutered, growing, senior, etc.
- Enter food calories — Enter the calories per kilogram (kcal/kg) listed on the food package.
- View the result — Press calculate to see the daily calorie needs and recommended food in grams.
How to calculate food portions with RER and MER
A pet's daily calorie need is calculated in two steps. First, find the RER (Resting Energy Requirement), the minimum energy needed at rest. RER is body weight raised to the power of 0.75, multiplied by 70 — a standard formula that reflects the metabolic difference between small and large animals.
Next, multiply RER by a factor for activity and life stage to get the MER (Maintenance Energy Requirement), the actual daily calorie need. Finally, divide MER by the food's calorie density (kcal/kg) to get the grams of food to give per day.
| Status | Factor (× RER) |
|---|---|
| Weight loss needed | 1.0 |
| Neutered adult cat | 1.2 |
| Neutered adult dog (indoor / low activity) | 1.2 – 1.4 |
| Neutered adult dog (normal) | 1.6 |
| Intact adult dog | 1.8 |
| Highly active dog | 2.0 – 5.0 |
| Growing puppy / kitten | 2.0 – 3.0 |
For example, a 5 kg neutered adult dog (factor 1.6) on 3,600 kcal/kg food gives RER = 70 × 5^0.75 ≈ 234 kcal, MER = 234 × 1.6 ≈ 374 kcal, and daily food = 374 ÷ 3600 × 1000 ≈ 104 g. Consult a veterinarian for an accurate diagnosis and diet.
Frequently asked questions (FAQ)
What are RER and MER?
RER (Resting Energy Requirement) is the minimum calories needed at rest, calculated as RER = 70 × body weight (kg) raised to the power of 0.75. MER (Maintenance Energy Requirement) is RER multiplied by an activity factor — the actual daily calorie need.
How do I choose the activity factor?
Use about 1.6 for a neutered adult dog, about 1.2 for a neutered adult cat, 2.0 to 5.0 for highly active dogs, 1.0 for weight loss, and 2.0 to 3.0 for growing puppies and kittens. Adjust the exact factor with your veterinarian.
Where do I find the calories per kilogram of food?
Check the 'metabolizable energy (ME)' or 'kcal/kg' figure on the food package. Typical dry foods are around 3,300 to 4,000 kcal/kg. If it is not listed, ask the manufacturer.
Can I feed exactly the calculated amount?
The result is an estimate for reference only. The actual amount depends on body condition score (BCS), treats, and health status, so monitor weight changes and adjust, and consult a veterinarian for an accurate diet.
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Last updated: 2026-06-25