Work out how many calories your dog or cat needs each day, and how many grams of their food that is.
A starting point for a healthy dog. Weigh them every few weeks and adjust if their weight changes.
How to use it
Vets start from the resting energy requirement (RER): the calories a pet burns at rest, worked out as 70 × body weight in kg to the power of 0.75. Daily needs are the RER multiplied by a factor for life stage and activity, such as 1.6 for a neutered adult dog or 1.2 for a neutered adult cat.
Find the energy content on your pet food’s label, usually as kcal per 100 g or per kg (divide kcal per kg by 10), and the calculator turns calories into grams a day. For weight loss it uses your pet’s target weight, which your vet can help you set.
If your pet needs to lose weight, aim for slow, steady loss and check in with your vet or nurse. Cats should never be starved to lose weight, as rapid weight loss can cause serious liver disease. Change foods gradually over a week to avoid stomach upsets.
It depends mostly on weight and activity. A neutered 10 kg dog needs roughly 630 kcal a day and a neutered 30 kg dog about 1,440 kcal. Active and working dogs need more, and less active dogs less.
A typical neutered 4 kg cat needs about 240 kcal a day. Indoor or less active cats may need nearer 200 kcal.
RER is the resting energy requirement, the energy needed at rest. MER, the maintenance energy requirement, is the RER multiplied by a factor for life stage and activity. Vets use both to plan feeding and weight loss.
Feeding guides on packs are averages for a range of weights and are often generous. Use this figure and the label’s energy content as a cross-check, then adjust using your pet’s weight and body shape.
These tools are planning aids, not a diagnosis or a replacement for veterinary advice. If a pet is unwell, has eaten something risky, or you are unsure what to do next, contact a vet.