Dry Matter Basis: How to Compare Cat Food Labels

A can of cat food that lists 11% protein and a bag of kibble that lists 34% protein look wildly different on the shelf, but that comparison is almost meaningless. The can is mostly water, and water carries no nutrients. Once you strip the moisture out and convert both foods to dry matter basisthose two numbers can flip completely, and the “low protein” canned food may turn out to be the more protein dense option. This guide shows you how to do that conversion in about a minute, with a worked calculator example you can copy for your own cat’s food.

What the Guaranteed Analysis on a Cat Food Label Really Says

The guaranteed analysis panel lists protein, fat, fiber, and moisture as percentages “as fed,” meaning as the food comes out of the package. Two things make it hard to use for comparison:

• Moisture varies enormously. Dry food is usually around 10% moisture. Canned food is often 75% to 82% moisture. Every nutrient percentage on the label is diluted by that water.
• They are minimums and maximums, not exact values. Protein and fat are listed as minimums, fiber and moisture as maximums. A food can legally contain more protein than the label states, so treat the panel as a rough range rather than a precise recipe.

That is why a “34% protein” kibble and an “11% protein” pate cannot be judged side by side until you put them on the same footing. Dry matter basis is that footing.

How to Convert Guaranteed Analysis to Dry Matter Basis

You only need subtraction and division. Here is the whole method:

1. Find the moisture percentage on the guaranteed analysis.
2. Subtract it from 100. That answer is the dry matter content of the food.
3. Turn that dry matter number into a decimal by dividing by 100. For example, 22% becomes 0.22.
4. Divide the nutrient percentage by that decimal. The result is the nutrient level on a dry matter basis.

A quick calculator example: a canned food shows 78% moisture and 11% protein. Dry matter is 100 minus 78, which equals 22. As a decimal that is 0.22. Then 11 divided by 0.22 equals 50. So the food is 50% protein on a dry matter basis, not 11%. Nothing about the food changed. You simply removed the water from the math.

Estimating carbohydrates by difference

Cat food labels rarely list carbohydrates, so you calculate them by subtracting everything else from 100: moisture, protein, fat, fiber, and ash. Ash is the mineral residue and is often left off the panel. If ash is missing, your carb estimate will come out higher than reality, so treat it as a loose figure. Our guide to wet versus dry cat food covers why that carb difference matters for cats in particular.

A Side by Side Example: Wet Food and Dry Food Compared

Here are two realistic label profiles run through the same math.

Dry food: 10% moisture, 32% protein, 15% fat, 4% fiber, 7% ash. Dry matter is 90%, or 0.90.

• Protein: 32 divided by 0.90 = 35.6% dry matter basis
• Fat: 15 divided by 0.90 = 16.7% dry matter basis
• Carbs: 100 minus 10 minus 32 minus 15 minus 4 minus 7 = 32% as fed, which is 35.6% dry matter basis

Canned food: 78% moisture, 11% protein, 6% fat, 1.5% fiber, 1.5% ash. Dry matter is 22%, or 0.22.

• Protein: 11 divided by 0.22 = 50% dry matter basis
• Fat: 6 divided by 0.22 = 27.3% dry matter basis
• Carbs: 100 minus 78 minus 11 minus 6 minus 1.5 minus 1.5 = 2% as fed, which is 9.1% dry matter basis

Read the label numbers alone and the kibble looks like the protein powerhouse. On a dry matter basis the canned food delivers more protein, more fat, and far fewer carbohydrates. That is the entire point of the exercise.

What the Numbers Mean for Your Cat

Cats are obligate carnivores, so most owners are looking for higher protein, moderate fat, and lower carbohydrate levels. On a dry matter basis, a rough benchmark for many adult maintenance foods is protein in the high 30s to 50s, fat somewhere in the teens to high 20s, and carbohydrates as low as the food can reasonably go. These are general guideposts, not rules, and they shift with life stage and health.

Kittens and pregnant or nursing cats need more energy and nutrients per bite, so the targets look different, and our guide to choosing food for kittens walks through what to prioritize. Indoor and less active cats often do better with a food where fat and calories are not at the top of the range, which we cover in best food for indoor cats.

If your cat has kidney disease, diabetes, urinary blockages, pancreatitis, or a weight problem, do not pick a food from a label calculation alone. Ask your vet for target ranges for your specific cat before you switch, and bring the label with you.

Common Mistakes When Comparing Cat Food on a Dry Matter Basis

• Forgetting fiber and ash in the carb estimate. Skip them and your carbohydrate figure will be inflated by several points.
• Comparing dry matter when you meant per calorie. Dry matter basis tells you nutrient density per unit of dry weight. For weight loss, portion size and calories per gram matter more, so check the calorie statement (often listed as kcal per kilogram or kcal per can) as well.
• Assuming higher protein is always better. Very high protein is not automatically right for every cat, especially seniors or cats with kidney concerns. Match the food to the cat, and confirm with your vet.
• Ignoring what the percentages cannot show. Two foods can both be 45% protein on a dry matter basis while using very different ingredients and digestibility.
• Forgetting treats and toppers. Extras can shift the whole diet, so keep them small and account for them.

One practical tip: if you are moving your cat toward more canned food after doing these comparisons, change the food gradually rather than all at once. Here is how to transition your cat to wet food without stomach trouble.

Beyond the Numbers: What the Label Will Not Tell You

Dry matter basis levels the playing field for protein, fat, and carbs, but it does not rank foods. Once two foods look similar on paper, check these:

• Life stage statement. Look for a clear statement that the food is complete and balanced for your cat’s life stage, based on a recognized nutrient profile or a feeding trial.
• Named animal sources. “Chicken” or “salmon” tells you more than a vague category name. Ingredients are listed by weight before processing, so use them as a sanity check, not a ranking system.
• Calorie density. A food with more calories per can means smaller portions and a lower cost per day, which often matters more than the sticker price.
• Your cat’s actual response. Stable weight, good muscle condition, a healthy coat, normal stool, and steady energy are the real test of whether a food works.

If a food produces vomiting, diarrhea, itching, or weight loss that does not settle within a week or so, stop guessing at labels and call your vet.