Pet Weight Loss & Weight Gain Calculator
Enter your pet's current and target weight to get a safe timeline and a starting daily calorie target.
Awaiting Details
Enter a current weight and a different target weight to see a plan.
How It Works & The Weight Management Formula
Veterinary weight-management protocols (WSAVA Global Nutrition Committee, Ohio State University Indoor Pet Initiative) recommend a safe rate of change of about 1-2% of body weight per week, with weight-loss plans starting around 80% of RER at current weight, and weight-gain plans starting around 110-120% of MER.
These are starting points, not fixed prescriptions -- reweigh every 2-4 weeks and adjust calories based on actual progress. Weight loss in cats needs particular caution, since overly rapid loss can trigger hepatic lipidosis, a serious liver condition.
Frequently Asked Questions
How fast should a pet safely lose or gain weight?
Veterinary weight-management guidelines (WSAVA, Ohio State Indoor Pet Initiative) recommend a safe rate of about 1-2% of body weight per week for both loss and gain. Faster changes increase the risk of muscle loss, nutritional deficiency, or (in cats) hepatic lipidosis.
How many calories should I feed for weight loss?
A common starting point is about 80% of the Resting Energy Requirement (RER) calculated at your pet's current weight, then adjusted based on actual progress. Never restrict calories drastically, especially in cats -- rapid weight loss in cats can cause a serious liver condition.
How many calories should I feed for weight gain?
A starting point is about 110-120% of maintenance calories (MER), increased gradually while monitoring body condition. Sudden large calorie increases can cause digestive upset.
Should I recheck my pet's weight during a weight plan?
Yes -- weigh your pet every 2-4 weeks and adjust calories based on actual progress rather than the initial estimate alone. Veterinary supervision is especially important for weight-loss plans in cats and for pets with existing health conditions.
Medical Disclaimer
This tool provides general, educational estimates and is not a substitute for professional veterinary advice, diagnosis, or treatment. Weight-loss and weight-gain plans should be supervised by a veterinarian, especially for cats, senior pets, or pets with existing health conditions. Always consult your veterinarian about your pet's specific health needs before making changes to their diet, water intake, or care routine.
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Calorie Calculator
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How This Calculator Works
Read the full breakdown of the formula, sources, and how to interpret your result.