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How do I work out the calories in pet food?

Calories are units of energy and it is important to know how many calories a dog or cat food provides so that daily feeding amounts can be calculated and the pet gets enough food for its life stage e.g.  Growth, pregnancy, nursing, maintenance or old age.

You should be able to contact the manufacturer of your pet food to get the calorie content per 100g of food and some foods will now have this information on the pack. However, we have created a 5 step guide to working it out yourself.

STEP 1 – find the analytical constituents

Turn over your packet, can or tray of dog or cat food and look for the section that says ‘Analytical Constituents’. Here you should find the percentage of protein, fat, fibre and ash (minerals). If the product contains 14% or more moisture then this will be labelled too. If moisture is not listed then assume it is about 8-10%.


STEP 2 – work out the carbohydrate level

The next step is to work out the carbohydrate level. To do this, you add up the protein, fat, fibre, ash and moisture and then substract the total from 100.

Carbohydrate = 100 - (protein 24% + Fat 14% + Fibre 3.5% + Ash 6.5% and moisture 8%)

So the carbohydrate level in this food is 44%.

STEP 3 – know your calories per gram

We now need to work out how many calories are coming from protein, fat and carbs. There is a simple way of doing this once you know that:

1 gram of protein provides 3.5 calories (Kcals)

1 gram of fat provides 8.5 calories (Kcals)

1 gram of carbohydrate provides 3.5 calories (Kcals)

STEP 4- work out how many calories come from each nutrient

We already know that in the example above the protein level is 24%, the fat level is 14% and the carbohydrate level is 44%. This means that in 100 grams of pet food there is 24 grams of protein, 14 grams of fat and 44 grams of carbohydrate. To get the total calories we multiply these figures by the amount of calories each gram provides.


Protein 24g x 3.5 (as 3.5 is how many calories are in 1 gram of protein) = 84 calories come from protein

Fat 14g x 8.5 (as there are 8.5 calories in 1 gram of fat) = 119 calories come from fat

Carbohydrate 44 x 3.5 (as there are 3.5 calories in 1 gram of fat) = 154 calories come from carbohydrate

STEP 5 – add up to get your final figure

Add up the calories from protein, fat and carbohydrate to get your total amount of calories:

84 + 119 + 196 = 357 

So there are 357 calories (Kcals) in 100g of this example pet food.

To find out how many calories your pet needs, read our next article here

How much should you give to your dog?

Use our simple, vet approved Calorie Calculator to help you get just the right amount of good stuff in those tummys.

Calorie Calculator