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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.

Enter Values

Species

Body weight (kg)

Neuter status

Activity level

Result

Enter values above and click Calculate to see your result.

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Our AI assistant provides general estimates and advice only. Please consult a qualified healthcare professional before making any health-related decisions.

Formula

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.

Review and Methodology

Updated Mar 28, 2026

This calculator runs locally in your browser. Inputs are converted into the units required by the formula, and the result is paired with supporting references so you can verify the method before using it for planning or estimates.

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.

Can I use this Pet RER Calculator on my own web page?

You can. Look for the "Embed" button near the top of this calculator. It lets you pick a size, border style, and color palette, then gives you an iframe tag to paste into any webpage. The widget is responsive, loads fast, and costs nothing. More details at calculory.com/services/embed-calculators.

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.

AI Assistant

Ask about this calculator

I can help you understand the pet rer calculator formula, interpret your results, and answer follow-up questions.

Try asking

Our AI assistant provides general estimates and advice only. Please consult a qualified healthcare professional before making any health-related decisions.

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