Pet Food Calculator

About the Pet Food Calculator

The feeding guide on a bag of pet food is a starting point, but it covers a wide range of animals with a single line per weight. A young, active, unneutered dog and an older neutered dog of the same weight can need very different amounts. Feeding too much is the most common problem: vets see more overweight dogs and cats than underweight ones, and extra weight shortens pets' lives and makes arthritis, diabetes and other conditions more likely.

This pet food calculator uses the method vets use. It works out your dog's or cat's daily calories from its weight and life stage, then turns that into cups and grams of food from the calorie figures on the label, split into meals. It also gives a sensible treat allowance.

How to Use the Pet Food Calculator

Choose dog or cat.

Enter your pet's weight in kilograms or pounds. For a pet that needs to lose weight, enter its ideal weight, not its current one.

Choose the life stage: neutered adult, intact adult, weight loss, active or working, growing puppy or kitten, or senior and inactive.

Enter the food's calories per cup and calories per kg, both usually printed on the label as kcal/cup and kcal/kg.

Enter the number of meals a day.

How Daily Calories Are Worked Out

  resting energy (RER)  =  70 × weight in kg ^ 0.75
  daily energy          =  RER × life-stage factor
  cups a day            =  daily energy ÷ kcal per cup
  grams a day           =  daily energy ÷ kcal per kg × 1,000
  treats                =  up to 10% of daily energy

Step-by-Step Example

A 20 kg neutered adult dog, food with 360 kcal per cup and 3,600 kcal per kg, two meals a day.

  Resting energy:  70 × 20^0.75             =  662 kcal
  Daily energy:    662 × 1.6                =  1,059 kcal
  Cups:            1,059 ÷ 360              =  2.94 cups  (1.47 per meal)
  Grams:           1,059 ÷ 3,600 × 1,000    =  294 g  (147 g per meal)
  Treats:          10% of 1,059             =  up to 106 kcal

A 4.5 kg neutered indoor cat.

  Resting energy:  70 × 4.5^0.75            =  216 kcal
  Daily energy:    216 × 1.2                =  260 kcal

Why Weight to the Power 0.75?

Energy needs do not rise in direct proportion to body weight. A dog twice as heavy does not need twice the food, because larger animals have less surface area relative to their volume and lose heat more slowly. Raising weight to the power of 0.75 — known as metabolic body weight — captures this well across species, from small cats to giant dogs. The factor then adjusts for activity, neutering and life stage.

Checking Body Condition

The calculation is a starting point. The real test is your pet's body. You should be able to feel the ribs easily under a thin layer of fat without seeing them, and see a waist from above and a tuck behind the ribs from the side. Weigh your pet every few weeks. If it is gaining weight, reduce the food by about 10 percent; if losing weight it should not, increase it by 10 percent. Vets use a nine-point body condition score and can help you judge it.

Weight Loss Safely

For an overweight pet, feed for the ideal weight using the weight loss factor, and aim to lose around 1 to 2 percent of body weight a week for dogs, and less for cats. Cats must never be starved or put on a crash diet: a fast weight loss can cause a dangerous liver condition called hepatic lipidosis. Always involve your vet in a weight loss plan, especially for cats and for pets with medical conditions.

Puppies, Kittens and Seniors

Growing animals need far more energy for their size than adults, and several small meals a day. Large-breed puppies need carefully controlled growth, so follow a large-breed puppy food and your vet's advice. Older pets often need fewer calories as they slow down, but some lose weight with age and need more; senior pets should be weighed regularly.

Wet and Dry Food Together

Many owners feed a mix of wet and dry food. To combine them, work out the daily calories, then decide how to split them — for example, half from each. Wet food is usually labelled in calories per can or pouch; divide your share of the calories by that figure to find how many to feed, and use the calculator's grams or cups for the dry share. Remember that wet food is mostly water, so a cat or dog eating a lot of wet food may drink less.

Measuring Food Accurately

A standard measuring cup is 8 US fluid ounces, but many pet food scoops are larger or smaller, and a heaped cup can hold 20 percent more than a level one. Weighing the food on a kitchen scale is the most accurate method, which is why the calculator also gives grams.

Understanding Your Result

Daily calories is the estimated energy your pet needs each day.

Cups gives the food in cups a day and per meal.

Grams gives the food by weight, which is more accurate than cups.

How it is worked out shows the resting energy and the factor used.

Treats gives the daily treat allowance.

Worth knowing explains how to adjust the amount.

When Should You Use This Calculator?

Changing to a new food with a different calorie content.

Bringing home a new pet.

Helping a pet lose weight, alongside your vet.

After neutering, when energy needs fall.

Checking whether the label amount is right for your pet.

Common Mistakes

Feeding for the current weight of an overweight pet.

Using cups without checking the calories per cup.

Forgetting treats and table scraps.

Not adjusting after neutering.

Crash dieting a cat.