Cat food labels don’t list carbohydrate content, but you can calculate it yourself with simple subtraction. All you need is the guaranteed analysis printed on the package and a calculator. The formula works because every ingredient in cat food falls into one of a few categories: protein, fat, fiber, moisture, and ash. Whatever percentage is left over after adding those up is carbohydrate.
Why Carbs Aren’t on the Label
Pet food regulations currently require manufacturers to list minimum crude protein, minimum crude fat, maximum crude fiber, and maximum moisture on the guaranteed analysis. Carbohydrates are not required. AAFCO (the organization that sets labeling standards) has drafted updated regulations that would include a “Total Carbohydrate” line on a new Pet Nutrition Facts box, but most products on shelves today still follow the older format. Manufacturers are also not allowed to make “low carbohydrate” claims on packaging, so even brands marketing to health-conscious cat owners can’t put that language on the bag or can.
The Basic Formula
The calculation is straightforward. Add up the percentages of protein, fat, fiber, moisture, and ash listed on the label, then subtract that total from 100. The remainder is the estimated carbohydrate percentage.
- Carbohydrate % = 100 − (protein + fat + fiber + moisture + ash)
There’s one catch: many labels don’t list ash. If it’s missing, use an estimate of 3% for canned food and 6% for dry food. These are standard approximations used by veterinary nutritionists.
Canned Food Example
Say a canned cat food lists 12% protein, 2% fat, 1.5% fiber, and 80% moisture. No ash is listed, so you use 3%. The math: 100 − (12 + 2 + 1.5 + 80 + 3) = 1.5% carbohydrate. That’s very low, which is typical for high-moisture canned foods on an “as-fed” basis.
Dry Food Example
A dry kibble lists 35% protein, 15% fat, 5% fiber, 12% moisture, and 6.8% ash. The calculation: 100 − (35 + 15 + 5 + 12 + 6.8) = 26.2% carbohydrate. Dry foods almost always come out higher because removing moisture concentrates everything, including the starches and fillers needed to hold kibble together.
Why These Numbers Are Estimates
The guaranteed analysis uses minimums for protein and fat, and maximums for fiber and moisture. These are not the actual amounts in the food. A label showing 24% minimum protein could mean the food contains 26% or even 32% protein. Since the carb calculation depends on subtracting these values from 100, any gap between the guaranteed and actual numbers shifts your carb estimate. A food with more protein than its guaranteed minimum, for example, actually has fewer carbs than your calculation suggests.
For a more accurate picture, call the manufacturer and ask for the “typical” or “average” nutrient analysis. Some companies will also provide values per 1,000 kilocalories, which makes comparing different products much easier. Tufts University’s veterinary nutrition team specifically recommends this approach for anyone trying to manage their cat’s diet precisely.
Comparing Products on a Dry Matter Basis
Comparing a canned food at 80% moisture to a dry food at 12% moisture using their label numbers is misleading. The canned food looks lower in everything simply because most of it is water. To compare fairly, you need to convert both to a “dry matter basis,” which strips out the water and shows you the nutrient concentration as if both foods were completely dry.
The conversion takes two steps. First, subtract the moisture percentage from 100 to get the dry matter percentage. Then divide the nutrient you’re interested in by that dry matter percentage and multiply by 100.
Using the canned food example above: it has 80% moisture, so its dry matter is 20%. The as-fed carb content was 1.5%. On a dry matter basis, that’s 1.5 ÷ 20 × 100 = 7.5% carbohydrate. For the dry food at 12% moisture, dry matter is 88%. Its carbs convert to 26.2 ÷ 88 × 100 = 29.8%. Now you have a meaningful comparison: 7.5% versus 29.8%.
Calculating Carbs as a Percentage of Calories
Weight-based percentages tell you one thing, but caloric contribution tells you another. Fat contains more than twice the calories per gram as protein or carbohydrate, so a food that looks moderate in fat by weight might get a large share of its calories from fat. To understand how much of your cat’s energy intake comes from carbs, you need to use the modified Atwater factors that AAFCO assigns to pet food: 3.5 calories per gram for both protein and carbohydrate, and 8.5 calories per gram for fat.
Take a dry food with 35% protein, 15% fat, and 26.2% carbohydrate (calculated above). Multiply each by its calorie factor: protein contributes 35 × 3.5 = 122.5, fat contributes 15 × 8.5 = 127.5, and carbs contribute 26.2 × 3.5 = 91.7. The total is 341.7. Carbohydrates account for 91.7 ÷ 341.7 × 100 = about 27% of the food’s calories. This caloric percentage is often more useful than the weight percentage when evaluating a diet’s impact on blood sugar or weight.
What These Numbers Mean for Your Cat
Cats are obligate carnivores. Research analyzing the natural diet of feral cats found that only about 2% of their daily calories come from carbohydrate, with 52% from protein and 46% from fat. On a dry matter basis, the carbohydrate content of a prey-based diet is roughly 2.8%. Most commercial dry cat foods contain ten times that amount or more.
This doesn’t mean all carbs are harmful, but the gap between a cat’s evolutionary diet and the contents of many commercial foods is significant. For diabetic cats specifically, the American Animal Hospital Association recommends limiting carbohydrates to approximately 12% of metabolizable energy. That’s a target your veterinarian can help you translate into specific food choices, but you can screen products yourself using the calculations above. If a food’s carbs account for 30% or more of its calories, it’s well above that threshold.
Canned and raw diets tend to fall in the 5 to 15% range on a dry matter basis. Most dry kibbles land between 25% and 50%, though some grain-free formulas come in lower. Running the numbers on whatever you’re currently feeding takes about two minutes and gives you a much clearer picture of what your cat is actually eating.