How to Calculate Carbohydrates in Dog Food: The Expert Guide
Carbohydrates are the most mysterious part of dog food. They are (almost) never listed on the label, but once you do the calculation, it turns out that they make up the bulk of many dog food formulas.
Why is it like that? Do dogs even need carbs? How does one accurately calculate the amount of carbohydrates in dog food?
We’ve asked experts in dog nutrition to help you detangle the mystery.
Related: The Best Dog Food Australia.
Related: How To Choose The Right Dog Food?
Related: How Is Australia’s Dog Food Industry Regulated?
Related: What is AAFCO? The Association of American Feed Control Officials.
Related: What Is the Pet Food Industry Association of Australia (PFIAA)?
Related: AAFCO vs PFIAA: Dog Food Standards Comparison Australia.
Related: Real Meat vs Meat Meal.
Calculating Carbohydrate Content in Dog Food
Calculating the (rough) percentage of carbs in dog food is fairly easy once you know what you are doing. Here is the process:
#1 Locate the Guaranteed Analysis
Every commercially sold dog food must contain a ‘guaranteed analysis’ section on the label. It’s usually located on the back of the packaging along with the ingredient lists. You’ll notice that the guaranteed analysis always lists the percentages of nutrients like fat and protein, but usually not carbs.
#2 Subtract the Percentages
According to our team of experts, the easiest way to find out the percentage of carbs in dog food is to find the percentages of everything else in the food and then assume that what’s left over is carbs.
So, you’ll need to take the percentages of protein, fat, fibre, ash and moisture and subtract that from 100. The number you get is the assumed percentage of carbohydrates in the dog food.
The technical term for the result you get in this way is “nitrogen free extract”, often also seen as “NFE”. We have yet to see this term on dog food packaging, but if you encounter it, this is what it means.
For example, here is the nutritional analysis of Petzyo’s Kangaroo & Sweet Potato recipe:
To get the amount of carbs, we’ll subtract all of these numbers from 100
100 - (27+11+7+5+9) = 41
The food contains 41%of carbohydrates.
#3 That’s It?
This was not that difficult, right? However, there are notable downsides to this method of calculation.
First of all, although it’s basic information, the moisture content and especially the ash content are not always listed on dog food packaging. You might have to do some digging to find that out. (Quick tip: sometimes the label on the packaging doesn’t list all the details, but the manufacturer’s website does, so make sure to check that). If you can’t find the info, you can assume the value is 5% for ash to get a rough estimate of carbs in your dog’s food.
Second, the guaranteed analysis doesn’t guarantee all that much. For protein and fat, the percentage listed is the minimum amount, whereas for fibre and moisture, you get the maximum amounts (2). The actual amounts in any batch of dog food can vary a lot. So, if a dog food features a minimum 20% of protein, it might actually have 25% which would throw off your carb calculation quite a bit.
Without going into too many details, there are a few more reasons why this method of calculation is not completely accurate. Still, most of the time it is a good enough estimate. Having a rough idea about the carb percentage is all you need to know most of the time. There is very limited value in knowing the exact number of calories that come from carbs in your dog’s food (a bit more on that below).
Comparing Carbohydrates in Dog Foods
The calculation we described above will give you an idea of how much carbs there are in a certain food in relation to protein and fat. But, if you want to compare two different dog foods, these numbers don’t mean very much at all! This is because of the water content in dog foods which can vary widely.
“Pet foods vary widely in their water content; most canned food contains about 80% water and dry food is only about 10% water. That means that if you’re comparing a dry food with a protein level of 33% from the guaranteed analysis to a canned food with a 8% protein level from the guaranteed analysis, the canned food seems much lower in protein. However, the protein levels are almost identical (at about 36%) when compared on a dry matter basis!” - Lisa M. Freeman, DVM, PhD, DACVIM (Nutrition); Petfoodology (2)
If you want to compare the carb content in two dog foods, first, do as above and get the percentage of carbs for each food.
Then, you’ll want to calculate the nutrient percentages on a dry matter basis in order to account for the water in the food. We do this by calculating the removal of water.
In the example above, we have calculated the percentage of carbs to be 41% and we can also see that the food contains 9% moisture.
For dry matter basis calculation we need to do this:
The food has 50% carbs on a dry matter basis.
If you do this calculation for each dog food formula you want to compare, you’ll get a fairly accurate percentage comparison even for different types of dog food.
Final Thoughts: Don’t Stress Too Much About the Numbers
As you have seen in this quick guide, getting a rough estimate of carbohydrates in your dog’s diet is easy. Finding out the exact amount of carbs, on the other hand, is very difficult (if not impossible) due to a range of factors. But that’s OK! Experts agree: the exact amount of carbohydrates in your canine companion’s bowl is not very important.
What’s way more important is the quality of ingredients that go into the food, and the numbers don’t tell us much about that. Just think about this: an apple has about the same amount of carbs as 5 teaspoons of sugar.
Which one would you rather feed your dog?
- Heinze, C.R. August 17, 2022. “All About Ash”. Petfoodology, TUFTS University. Retrieved August 7, 2023. https://vetnutrition.tufts.edu/2022/08/all-about-ash/
- Freeman, L.M. December 28, 2020. “What Is Guaranteed about the Guaranteed Analysis?”. Petfoodology. TUFTS University. Retrieved August 7, 2023. https://vetnutrition.tufts.edu/2020/12/what-is-guaranteed-about-the-guaranteed-analysis/