How are a cat's daily calories calculated?

The tool computes the resting energy requirement as 70 times body weight in kilograms raised to the power 0.75, then multiplies by a life-stage, neuter, and weight-goal factor to get the daily energy requirement. That calorie figure is then converted to grams of food.

Why convert to grams rather than cups?

Cat food, especially wet food, is far more accurately measured by weight than by volume. A kitchen scale removes the guesswork of partly filled cups, which is important because cats need precise portions and gain weight easily.

How do I find my food's calorie density?

Look for the metabolisable energy, often shown as calories per 100 grams or per can, on the label or the maker's website. Wet foods are typically 70 to 100 calories per 100 grams and dry foods 350 to 400, but check your specific product.

My cat needs to lose weight — is this safe?

The weight-loss setting reduces calories to about 80 percent of maintenance. Cats must lose weight slowly, no more than about 0.5 to 2 percent of body weight per week, because rapid loss can cause a dangerous liver condition called hepatic lipidosis. Work with your vet for obese cats.

Can I feed both wet and dry?

Yes. The tool shows the grams needed if feeding only wet or only dry. For a mix, split the daily calories between the two and weigh each portion to the proportional gram amount so the total still hits the calorie target.

Cat Food Daily Portion Calculator

Precise portions keep cats at a healthy weight

Cats are small, so even a little overfeeding adds up fast — feline obesity is common and drives diabetes and joint disease. This calculator uses the veterinary resting energy formula and converts the calorie target into grams of wet or dry food, which is far more accurate than measuring by the cup.

How it works

The foundation is the resting energy requirement:

RER = 70 × (body weight in kg) ^ 0.75

This is the energy a cat uses at complete rest. Multiplying by a life-stage factor (kittens need much more), a neuter factor (intact cats burn more), and a weight-goal factor gives the daily energy requirement. To turn calories into food, the tool divides the daily calories by the food’s calories per 100 grams and multiplies by 100:

grams = (daily calories ÷ calories per 100 g) × 100

Example

A neutered 4 kg adult cat at maintenance: RER = 70 × 4^0.75 ≈ 198 calories. With an adult neutered factor near 1.2 the daily target is about 238 calories. Fed only wet food at 80 calories per 100 grams, that is roughly 298 grams per day; fed only dry at 380 calories per 100 grams, about 63 grams.

Notes

Use this as a starting estimate and weigh portions on a kitchen scale. For weight loss, reduce slowly and reassess monthly — never crash-diet a cat, as rapid weight loss risks fatal liver disease. Senior cats may need more, not fewer, calories if they begin losing condition, so re-check the life-stage setting as your cat ages.