Pet Calorie (RER/MER) Calculator
Get your pet's exact daily calorie needs using veterinary-standard RER and MER formulas. Works for dogs and cats of all ages, sizes, and activity levels.
Body Condition Score (BCS): 5/9
Ideal — ribs palpable, slight waist visible from above
How to use Pet Calorie (RER/MER) Calculator
Calculate the daily calorie needs for your dog or cat based on the National Research Council (NRC) energy requirements. Proper calorie management is the single most effective way to prevent obesity — the most common preventable health problem in pets. This calculator gives you a personalised daily calorie target in kcal (kilocalories) that you can match to the caloric density of any pet food.
- Select species: dog or cat.
- Enter body weight (current) and ideal weight if different.
- Select life stage: puppy/kitten, adult, senior.
- Select reproductive status: intact or spayed/neutered.
- Select activity level and whether your pet is primarily indoor or outdoor.
- The result shows daily kcal target, MER, and portion guides at common food densities.
Your data never leaves your device — 100% private processing.
Daily calorie needs by pet weight and life stage
Energy requirements scale with metabolic weight (body weight^0.75) rather than linearly. This means a 10 kg dog needs less than twice the calories of a 5 kg dog. Neutering reduces energy requirements by approximately 15–25% compared to intact pets of the same weight and activity level. Overweight pets should be fed at their ideal weight's RER, not their actual weight, to facilitate gradual safe weight loss of 1–2% body weight per week.
| Pet weight | Dog daily kcal (avg activity) | Cat daily kcal (indoor) |
|---|---|---|
| 2 kg (4.4 lb) | 140 | 100 |
| 4 kg (8.8 lb) | 235 | 160 |
| 6 kg (13.2 lb) | 314 | 210 |
| 8 kg (17.6 lb) | 389 | 258 |
| 10 kg (22 lb) | 460 | — |
| 15 kg (33 lb) | 620 | — |
| 20 kg (44 lb) | 775 | — |
| 30 kg (66 lb) | 1,060 | — |
Signs your pet may be overweight and how to respond
The ribs test is the quickest at-home assessment: you should be able to feel your pet's ribs easily with light pressure but not see them. If you have to press hard to feel them, your pet is likely overweight. Additional signs include a rounded belly with no waist definition and difficulty grooming (in cats). The most effective intervention is controlled meal portions combined with measured weigh-ins every 2–4 weeks. Increase exercise gradually; avoid crash diets that can cause dangerous hepatic lipidosis in cats.
Glossary
- Metabolic weight
- Body weight raised to the power 0.75, used as the basis for RER calculation because it more accurately reflects metabolic rate than linear weight.
- Kcal
- Kilocalorie — the standard unit of food energy for both human and pet nutrition, often called a "calorie" colloquially.
- Safe weight loss rate
- For pets, 1–2% body weight per week is the maximum safe weight loss rate to preserve muscle mass.
- Hepatic lipidosis
- A potentially fatal liver condition in cats triggered by rapid weight loss or food deprivation — also called "fatty liver disease".
Related reading
Frequently Asked Questions
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Why use Pet Calorie (RER/MER) Calculator?
- Formulas verified against veterinary guidelines
- Covers dogs, cats, and other common pets
- Results include age equivalents and care tips
- No account or login — instant results
Common use cases
- Calculate your pet's age in human years
- Find the right food portion size for your dog's weight
- Estimate calorie needs for an overweight cat
- Look up safe and toxic foods for your pet
- Calculate a dog's ideal body weight range by breed
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