What Is a Pet Weight Loss Calorie Target Calculator?
This calculator estimates how many calories your dog or cat needs to maintain their current weight, then applies a standard 20% deficit to give you a safe daily calorie target for gradual weight loss. It uses the same Resting Energy Requirement (RER) formula veterinary nutritionists use as a starting point for feeding plans.
Gradual weight loss — typically 1–2% of body weight per week — is safer for pets than aggressive calorie cuts, which can cause nutrient deficiencies or, in cats especially, a dangerous liver condition called hepatic lipidosis.
How to Read Your Results
Resting Energy Requirement (RER)
This is the baseline number of calories your pet burns at rest, based purely on their current body weight using the formula 70 × (weight in kg)^0.75.
Estimated Maintenance Calories
RER multiplied by your selected activity factor gives an estimate of how many calories your pet burns in a typical day, including normal activity.
Daily Calorie Target for Weight Loss
This is your maintenance estimate reduced by 20% — a widely used starting deficit that supports steady fat loss while preserving lean muscle.
Real-World Example
A 40 lb, neutered adult dog with typical activity would calculate as follows:
| Step | Calculation | Result |
|---|---|---|
| Weight in kg | 40 × 0.4536 | ≈18.1 kg |
| RER | 70 × 18.1^0.75 | ≈620 kcal/day |
| Maintenance (× 1.6) | 620 × 1.6 | ≈992 kcal/day |
| Weight-loss target (× 0.80) | 992 × 0.80 | ≈794 kcal/day |
That works out to roughly 794 kcal per day — a moderate, sustainable deficit for gradual weight loss in a dog that size.
Tips for Safe Pet Weight Loss
- Weigh your pet every 1–2 weeks and aim for about 1–2% body weight loss per week.
- Include treats in the daily total — treats should stay under about 10% of total daily calories.
- Never apply a steep calorie cut to a cat without veterinary supervision, since rapid weight loss in cats carries real health risks.
- Re-check the target as weight drops, since maintenance calories fall as body weight decreases.
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Last updated: August 2026 · Reviewed by: Simple Calculator Tools Editorial Team