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.

What is the Cat Food Daily Portion Calculator?

Compute your cat's resting energy requirement from body weight in kilograms raised to the 0.75 power times 70, apply a life-stage and weight-goal factor, then convert to grams of wet or dry food. For cat owners managing portions and weight. It runs free in your browser on Gera Tools, with nothing uploaded.

Cat Food Daily Portion Calculator

Name: Cat Food Daily Portion Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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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.

When to use this calculator

You suspect your cat is slowly gaining weight and want to know how many grams to serve each day.
Your vet has recommended a weight-loss plan and you need to translate a calorie target into a measurable portion.
You have switched to a new food with a different calorie density and want to adjust the portion size without guessing.
You have multiple cats with different life stages and need to calculate separate portions for each.

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

Worked examples

Example 1 — neutered adult at maintenance A neutered 4 kg adult cat: 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 food at 380 calories per 100 grams, about 63 grams per day.

Example 2 — neutered adult on a weight-loss plan The same 4 kg cat but using a weight-loss factor of 0.8 gives a daily target of about 190 calories. At 80 kcal per 100 g wet food, that is roughly 238 grams — about 60 grams less than maintenance. The portion drops noticeably but avoids the hepatic lipidosis risk of cutting more aggressively.

Example 3 — finding the calorie density of your food Look on the label for “metabolisable energy” expressed as kcal/100 g or kcal per can. Wet foods commonly run 70–100 kcal/100 g; dry foods commonly run 340–420 kcal/100 g. If the label lists only kcal per can, divide by the can’s net weight in grams to get kcal/100 g.

Common mistakes and tips

Measuring by cup instead of weight. A cup of dry kibble varies widely by piece size and how packed the cup is. A kitchen scale gives a consistent gram reading every time.
Using the manufacturer’s serving guide as the target. Bag guidelines are often generous and designed for an average intact adult — they may not suit your neutered or senior cat.
Ignoring treats. Treats carry calories and should count toward the daily budget. A handful of treats per day can easily add 30–60 calories, enough to tip a small cat into slow weight gain.
Adjusting too rarely. Reweigh your cat monthly and recalculate. A cat who loses 0.3 kg will have a lower RER and needs a slightly smaller portion to keep losing at a safe pace.