A calculator is useful for starting a conversation, but feeding plans can become medical decisions.
Seek veterinary advice for pets that are underweight, obese, pregnant, lactating, diabetic, kidney-compromised, heart-compromised, recovering from illness, or younger than expected for their size. Rapid weight loss is particularly dangerous in cats.
Recheck weight and body condition every two to four weeks after changing portions. Weekly trend bands are useful for spotting direction, but adjust gradually rather than making dramatic cuts, and include treats, toppers, chews, and table food in the daily calorie total.