How Many Calories Does My Cat Need?
- Rachel
- Sep 23
- 6 min read
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In this article:
How Many Calories Do Cats Need?
When it comes to cats and calories, it's important to recognise the many factors that affect their energy levels and requirements. Some of these we can incorporate into our calculations, while others require a more specialist approach.
Here are some examples:
Age
Kittens need more energy and therefore more calories to support growth and development. When feeding commercial food, you'd normally give them a kitten formula to meet these requirements.
As cats age, their metabolism and activity levels slow down so they need fewer calories but higher quality protein to help combat muscle wastage. A specialised senior diet can be beneficial and reduce the risk of malnutrition.
Pregnancy
Pregnant cats require more calories and protein. Throughout the duration of their pregnancy, their food intake increases up to twice the amount of what they'd normally be eating. This increases further during lactation up to six times!
Neutered/spayed status
A cat's metabolism slows down after sterilisation due to hormonal changes, which means they need fewer calories to maintain their energy levels. It also affects appetite-regulating hormones, so you may notice that they're hungrier than usual. Studies show that male cats eat about 50% more post-operation. They also become less active, which causes many cats to gain weight.
Exercise
Indoor cats are generally more sedentary than those with outdoor access. Likewise, outdoor cats need extra fat during the winter months. You might have seen commercial food tailored to indoor cats with adjusted nutrient contents that take into account inactivity, metabolism and urinary health.
Related post: 5 Indoor Cat Foods Rated: Are They Really Worth it?
This article is intended for healthy adult cats over 2kg and up to 45kg. It's highly unlikely that you have a cat this heavy, but the formula can be applied to dogs of the same criteria.
This formula is not suitable for pregnant or lactating cats. If you have a senior cat or feed a prescription diet, you should consult a vet for advice.
For kittens, see the dedicated sections.
Resting Energy Requirements
Resting energy requirements (RER) refers to the amount of energy that cats require for maintaining basic bodily functions.
Simply, RER = kcal/day (how many calories your cat needs per day as a bare minimum).
*For the purpose of this article, kcal simply refers to calories.
Spritool Pet Scale for small to medium pets under 30kg. Features advanced sensors for high accuracy and a hold button to lock in weight when your pet stops moving. Measures in kg, lb, oz and grams.
Calculate RER
Step 1:
Accurately weigh your cat on a pet or baby scale like the one pictured above. You can use normal scales by weighing yourself holding kitty and weighing yourself separately, then deducting the difference. Depending on scale sensitivity, this should give you a rough estimate.
Step 2:
Calculate RER with the standard formula as used by veterinarians (adult cats only):
RER = 30 x (body weight in kg) + 70
Example: Drax weighs 5 kg.
30 x 5 (kg) = 150
150 + 70 = 220
This means that Drax's resting energy requirement is 220 calories per day.
Kitten RER
The formula for kittens under 2kg (or pets over 45kg) is slightly different:
70 x (body weight in kg) 3^4
OR
√√ (BW in kg x BW in kg x BW in kg) x 70
In this example, we'll be using the second formula because it's easier to break down and I prefer it.
Mini weighs 1.45 kg.
Using a calculator:
1.45 x 1.45 x 1.45 = 3.04
Now type in the following:
√√ 3.04 = (1.32)
1.32 x 70 = 92.4
Mini's RER is 92.4 calories per day.
Next, we can use these numbers to determine your cat or kitten's total energy requirements.
Total Energy Requirements
Total energy requirements (TER) can also be referred to as maintenance energy requirements (MER). This represents the adjustments you'll need to make to your cat's daily calorie intake based on variations like age, sex, activity levels, body condition and neutered/spayed status.
There are cat calorie calculators online that may factor in some or all of the above, which I'll link down below. As a general guide, you can work out the most common variations using the following formulas:
Normal/active neutered or spayed adult cats | RER x 1.2 |
Normal/active non-neutered or non-spayed adult cats | RER x 1.4 |
Underweight adult cats | RER x 1.8 |
Overweight adult cats (where the goal is weight loss) | RER x 0.8 |
Inactive/obese prone adult cats (not overweight) | RER x 1.0 |
Kittens aged 0-4 months | RER x 2.5 |
Kittens aged 4-12 months | RER x 2.0 |
Calculate TER
Using the example above, we already know that Drax's RER is 220 calories per day.
Drax falls into the category of a normal/active neutered adult cat = RER x 1.2
220 (calories) x 1.2 = 264
Drax's total energy requirements are 264 calories per day.
It's important to note that this is just an estimate and doesn't take into account every single variation or the individual cat. Some vets use a more generalised RER calculator as shown in the image below.
We can see from the table that the RER for a 5kg cat is 234 calories, which is slightly more than the 220 calories using the standard formula. Since these are recommendations only, information will vary from source to source - which is why it's crucial to monitor your cat's weight.
If you're worried or unsure about how much to feed your cat, the best person to advise you is a vet who can do a physical examination in order to determine health and body condition.
Here are some handy online calculators that are free and simple to use:
Cat Body Condition Score
Sometimes it's hard to tell if a cat is under or overweight due to their thick fluffy coats, and many owners don't know how much their cats should weigh. To help with this, you can use what's known as the Body Condition Score, as pictured below.
If you decide to use an online calculator for working out calorie intake (TER) then you'll likely need to familiarise yourself with this, and it's useful to know in general.
The Body Condition Score chart uses a combination of visual checks and touch to assess fat and muscle coverage. This helps to determine whether a cat is underweight, overweight or at an ideal body condition.
The Association for Pet Obesity Prevention is a great resource and provides a step-by-step guide for owners to follow at home.
Calculating Portion Sizes
Once you know your cat's recommended calorie intake or TER, you can create tailored portion sizes. In the UK, the calorie content of cat food isn't usually stated on the packaging - this is something else we have to work out.
For reference, see this dedicated post: How to Calculate the Calorie Content of Cat Food
Example:
Drax requires 264 kcal per day. His food contains 350 calories per 100g.
First, we need to calculate the calories per gram of cat food.
350 (calories) / 100g = 3.5
So, 1 gram provides 3.5 calories.
Since Drax needs 264 kcal per day:
264 / 3.5 = 75.42
Drax should be fed approximately 75 grams of the example cat food.
Lastly, divide this number by the amount of meals your cat has per day.
If Drax has 2 meals then I'd give him 37 grams per portion.
Note that this doesn't factor in treats, which should be deducted from TER and make up less than 10% of a cat's diet.
I hope this article has been of use and, remember, your local vet is always on hand to give you more personalised advice regarding your pet's diet. They might also recommend a qualified veterinary nutritionist who can guide you through the process of developing a suitable meal plan.
*All calculations are estimates. Actual calorie requirements may vary, but these guidelines are a good starting point for understanding a cat's basic nutritional needs.
Drop a comment to let us know if this helped you or your kitty!
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