How to Calculate Carbohydrates in Cat Food and Understanding Dry Matter Basis
- Rachel
- Sep 3
- 5 min read
Updated: Oct 24
In this article:
How many carbohydrates are in your cat's food?
You won't find the answer on a packaging label, or anywhere for that matter. Since carbohydrates aren't necessary in a cat's diet, manufacturers aren't required to disclose this information, despite most dry foods containing an average of 30-40%.
Sources of carbohydrates like veggies and grains are cheaper than using animal-based protein. A wild cat gets everything it needs from the meat, organs and bones of prey - including a very small amount of plant matter from the stomachs of animals. This would already be partially digested and therefore easier for a cat's body to break down.
The ingredients in commercial food must be heavily processed, which proves the point that carbohydrates are unsuitable for cats. They're mainly used as fillers to bulk out food and can contribute to weight gain, diabetes, allergies, urinary tract disease and other health issues.
Carbohydrates are a highly debated topic, but if you want to learn more then it's all broken down in this eye-opening post: Cats and Carbohydrates: Is Dry Cat Food Bad for Cats?
Regardless of opinion, we should be aiming to feed our cats as close to a natural diet as possible, which means paying attention to those carbohydrate levels. Once we know that, we can work out the total calorie content.
There's nothing wrong with contacting the manufacturer to get this information, but you could be waiting a long time for a response. With a few simple calculations, we can smash through this lack of transparency and discover the truth about what we're feeding our cats to make more informed decisions.
How to Calculate Carbohydrate Content
Let's look at the formula for working out carbohydrates per 100g of cat food.
Step 1:
Look for the "analytical constituents" section on your cat food label or packaging and note the percentage of protein, fat, fibre, ash and moisture.
Technically, moisture only has to be listed if it's greater than 14%. This won't be a problem with wet food, but if dry food doesn't state the moisture content then you can either contact the manufacturer or assume it's between 8-10%.
Step 2:
Once you have these numbers, add them all up and subtract the total from 100.
Using the image above as a reference:
36.5% (protein) + 12% (fat) + 6.9% (fibre) + 6.4% (ash) + 8% (moisture) = 69.8%
100 - 69.8 = 30.2
So, the carbohydrate level in this dry food is 30.2%.
It’s important to learn how to compare this to wet food as the results will appear significantly different.
Using the same formula:
12% (protein) + 2.6% (fat) + 0.05% (fibre) + 1.7% (ash) + 81.5% (moisture) = 97.85%
100 - 97.85 = 2.15
The carbohydrate level in this wet food is 2.15%.
By contrast, it seems as though wet food has a lower amount of protein, fat, fibre and ash due to the higher moisture content. The percentages shown on a cat food label are "as fed" which gives us the nutrient values with moisture included. For a true comparison, we have to remove the moisture to find what's known as the "dry matter basis" or DMB.
Dry Matter Basis
Use the following formula for calculating food on a DMB. For reference, I'm using the same wet food as pictured above.
Step 1:
Subtract the moisture content from 100.
100 - 81.5% = 18.5
This means the total percentage of food that isn't moisture is 18.5%.
Step 2:
Divide the "as fed" percentages shown on the label by the dry matter percentage we've just calculated (18.5%) then multiply the result by 100.
*Results rounded to the nearest whole number for ease.
Protein:
12% / 18.5 = 0.64 x 100 = 64
The amount of protein on a DMB is 64%.
Fat:
2.6% / 18.5 = 0.14 x 100 = 14
The amount of fat on a DMB is 14%.
Fibre:
0.05% / 18.5 = 0.002 x 100 = 0.2
The amount of fibre on a DMB is 0.2%
Ash:
1.7% / 18.5 = 0.09 x 100 = 9
The amount of ash on a DMB is 9%
Carbohydrates:
2.15% / 18.5 = 0.11 x 100 = 11
The amount of carbohydrates on a DMB is 11%
The same formula can be used on dry food, which is why it's important to find out the exact moisture content, if possible. You can see the results displayed in the table below, which gives us a fairer comparison of wet and dry food.
Dry Food | Wet Food |
Protein: 39% | Protein: 64% |
Fat: 13% | Fat: 14% |
Fibre: 7% | Fibre: 0.2% |
Ash: 6% | Ash: 9% |
Carbohydrates: 32% | Carbohydrates: 11% |
*Percentages as DMB
If you'd prefer a quicker option, there are plenty of carbohydrate and/or dry matter basis calculators online; but it never hurts to understand the mathematics so you can double check if necessary.
I like this carb calculator from Caticles that's simple to use, with helpful instructions and feeding tips.
For converting nutrients to a dry matter basis, you can use this calculator from the Feline Nutrition Center.
To learn more about your cat's energy needs and requirements, check out this helpful post: How Many Calories Does My Cat Need?
Summary
While there are lots of factors to consider when choosing a quality cat food, from vitamins and minerals to additives and preservatives, this should give you a basic understanding of the key nutrients that are essential for a cat's survival.
Commercial pet foods are formulated to be nutritionally balanced according to guidelines set by the FEDIAF (European Pet Food Industry) or AAFCO in the States. However, don't be fooled into thinking these guidelines are designed for cats to thrive at peak health. Rather, they're the minimum requirements to maintain basic bodily functions.
As a reference point, the FEDIAF guidelines for a complete food for adult cats are:
Protein: 26% (DMB)
Fat: 9% (DMB)
Fibre: no minimum requirement for carbohydrates.
Compared to a natural diet in the wild, which consists of approximately:
Protein: 55%
Fat: 43-44%
Fibre: 1-2%
These numbers vary slightly depending on source but, nevertheless, it explains why commercial food is so carb heavy. Grains and vegetables are used to make up for the substantial lack of animal protein and fat, which is a greater energy source than any other nutrient.
If you need more convincing, remember that a mouse is made up of 70% water. Cats restricted to a dry food diet are at serious risk of dehydration, on top of other deficiencies caused by low animal protein substituted with an excessive amount of carbohydrates.
For a more natural and species-appropriate diet, you might consider raw feeding or a fresh cat food company like KatKin. Find out more here: Fresh Raw and Cooked Cat Food: Tailor-Made Nutrition Sent to Your Door!
Did you find this carb calculator helpful? Has it changed the way you feed your cats?
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