Hi stranger! Signing up for MypetMD is easy, free and puts the most relevant content at your fingertips.

Get Instant Access To

  • 24/7 alerts for pet-related recalls

  • Your own library of articles, blogs, and favorite pet names

  • Tools designed to keep your pets happy and healthy

or Connect with Facebook

By joining petMD, you agree to the Privacy Policy.

petMD Blogs

Written by leading veterinarians to provide you with the information you need to care for your pets.

Subscribe to
Nutrition Nuggets
Your cat's nutrition is important for a healthy & happy life. petMD experts help you to know what to feed your cat, how much food to feed, and the differences in cat foods, so your cat gets optimum nutrition.
Nutrition Nuggets is the newest offshoot of petMD's Cat Nutrition Center. Each week Dr. Coates will use her expertise and wisdom to blog about the intricacies of cat nutrition.

Using Math to Compare Carbs in Canned Cat Food and Dry Food

December 06, 2013 / (2) comments

Whenever the topic of feeding cats comes up, a few points always seem to arise.


  1. Cats should eat high protein, moderate fat, low carbohydrate foods.
  2. For some individuals (e.g., those prone to obesity, diabetes mellitus, and many disorders of the kidneys and lower urinary tract) canned food is superior to dry.


However, when comparing cat food labels, those two statements can appear to be contradictory. I pulled the following guaranteed analyses off the website of a major pet food manufacturer. Both the canned and dry cat food formulations are chicken-based to make them as similar as possible


Canned Cat Food

Crude Protein, minimum

10.00 %

Crude Fat, minimum

5.00 %

Crude Fiber, maximum

1.00 %

Moisture, maximum

78.00 %

Ash, maximum

3.20 %


Dry Cat Food

Crude Protein, minimum

33. 00 %

Crude Fat, minimum

15. 00 %

Crude Fiber, maximum

3. 00 %

Moisture, maximum

10. 00 %

Ash, maximum

7. 00 %


At first glance, doesn’t it look like the dry cat food better fits the high protein, low carb (I know it’s not listed, more on that in a sec), moderate fat mantra? But that all changes when you take water out of the equation. Look at those wildly different moisture levels. When you calculate the foods’ guaranteed analyses on a dry matter basis (removing the water), you see that high protein, low carb, and moderate fat and a canned formulation typically go hand-in-hand.


To reconfigure a guaranteed analysis on a dry matter basis, follow these steps.


  1. Find the percent moisture and subtract that number from 100. This is the percent dry matter for the food.
  2. Divide each nutrient percentage on the label by the percent dry matter for the food and multiply by 100.
  3. The resulting number is the nutrient percentage on a dry matter basis.


When we do this for the two guaranteed analyses listed above, these are the results.


Canned Cat Food

Crude Protein, minimum

45.45 %

Crude Fat, minimum

22.73 %

Crude Fiber, maximum

4.55 %

Moisture, maximum

0 %

Ash, maximum

14.5 %


Dry Cat Food

Crude Protein, minimum

36.67 %

Crude Fat, minimum

16.67 %

Crude Fiber, maximum

3.33 %

Moisture, maximum

0 %

Ash, maximum

7.78 %


Once you’ve converted the guaranteed analysis to dry matter basis, you can easily calculate the carbohydrate content of any food based on the idea that the only thing left once protein, fat, fiber, moisture, and ash have been accounted for are starches and sugars.


Therefore, the carbohydrate content of the canned food in our example is


                100 – (45.45 + 22.73 + 4.55 + 0 + 14.5) = 12.77%


And for our dry food it is


                100 – (36.67 + 16.67 + 3.33 + 0 + 7.78) = 35.55%


The dry food contains almost three times the amount of sugars and starches in comparison to the canned food. Amazing what some math can reveal, eh?


Dr. Jennifer Coates


Image: Thinkstock


Subscribe to Nutrition Nuggets

Comments  2

Leave Comment
  • Numb3rs
    12/06/2013 04:39pm

    I wonder if Charlie Eppes ever did any math on pet foods. :-)

  • 03/02/2014 03:53pm

    This is great to know and so very useful when choosing pet food.
    My cat was diagnosed with diabetes just over a year ago. I had him on diabetic dry food from the vet upon initial diagnosis and then slowly switched to only canned wet food. This change in diet is why he is now in remission. His weight is normal and so is his glucose level.




Photo of Jennifer

... graduated with honors from the Virginia-Maryland Regional College of Veterinary Medicine in 1999. In the years since, she has practiced veterinary medicine in Virginia, Wyoming, and Colorado. She is the author of several books about veterinary medicine and animal care, including the Dictionary of Veterinary Terms, Vet-Speak Deciphered for the Non-Veterinarian .

Jennifer also writes short stories that focus on the strength and importance of the human-animal bond and freelance articles relating to a variety of animal care and veterinary topics. Dr. Coates lives in Fort Collins, Colorado with her husband, daughter, and pets.

  • Lifetime Credits:
  • Today's Credits:
Hurry Before All Seats are Taken!
Be an A++ Pet Parent! Take fun & free courses to earn badges & certifications. Choose a course»


When did your cat last have a routine vet checkup?

* In the past 1 year
* In the past 2 years
* In the past 3 years
* More than 3 years ago