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Pet RER Calculator

Pet RER calculator estimates resting energy requirement (RER) in kcal per day for dogs and cats using body weight, then applies a maintenance factor for neuter status and activity. Use it to compare feeding plans to food labels in 2026; your veterinarian should confirm targets.

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Formula

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Core Formula
RER (kcal/day) = 70 × (body weight in kg)^0.75Maintenance (MER) ≈ RER × activity factor (species, neuter status, and activity)

How it works: RER is the baseline metabolic need at rest. Real feeding plans also use life stage, body condition score, therapeutic diets, and treats, which this simplified factor model cannot capture fully.

Worked Example

Example: 20 kg neutered dog, moderate activity.
1Step 1: RER = 70 × 20^0.75, about 662 kcal/day.
2Step 2: For a neutered dog with moderate activity, a common combined factor is near 1.8.
3Step 3: MER ≈ 662 × 1.8 ≈ 1,192 kcal/day.
4Step 4: Split that total across meals using your food label kcal per cup and your veterinarian body condition goals.

RER and daily feeding

Resting energy requirement estimates calories needed at rest. Maintenance energy multiplies RER so the total matches typical daily life.

  • Body condition scoring often matters more than a single calorie number on day one
  • Neutered pets often need fewer calories than intact pets at the same weight
  • Indoor cats frequently need careful calorie control to avoid weight gain
  • Therapeutic foods and medical conditions change targets beyond this generic model

Use this tool as a starting point for conversations with your veterinary team, not as a prescription.

You can also calculate changes using our Dog Chocolate Toxicity Calculator, Benadryl Dosage for Dogs Calculator, Calorie Calculator or BMR Calculator.

Frequently Asked Questions

Is RER the same as the calories on my food bag?

Food labels show kcal per cup or per can. This calculator estimates how many total kcal your pet may need per day so you can compare portions to the label.

Why use 70 times weight to the 0.75?

It is a widely taught exponential form for metabolic size scaling in dogs and cats. Your clinic may use a slightly different reference.

My pet needs to lose weight. Should I use MER from this tool?

Weight loss plans often use a reduced percentage of current or ideal maintenance calories. Ask your veterinarian for a safe deficit.

Does activity level matter for an indoor cat?

Yes, but many indoor cats are closer to sedentary unless you add structured play. Your veterinarian can help classify activity.

Are puppies and kittens covered?

Growing animals have higher needs per kg than adults. This adult-oriented model is not meant for growth life stages.

Can I use pounds instead of kg?

Convert pounds to kg first (divide pounds by about 2.20462), then enter kg for this tool.

Medical Disclaimer

This calculator is provided for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any decisions based on these results. Do not disregard or delay seeking medical advice because of information obtained from this tool.

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