Dry Matter Basis in Pet Food: How to Compare Dog & Cat Food

What Is Dry Matter Basis in Pet Food?

Every pet food label carries a “Guaranteed Analysis” panel listing nutrient percentages such as crude protein, crude fat, crude fiber, and moisture. Those percentages are given “as fed” — meaning they include whatever water is actually in the food, exactly as it comes out of the can or bag.

Dry matter is simply everything left in the food once water is set aside: the protein, fat, fiber, carbohydrate, and minerals. “Dry matter basis” (often abbreviated DMB) means recalculating each nutrient as a percentage of that dry portion only, rather than as a percentage of the whole (wet-plus-dry) food. This matters because the guaranteed analysis only requires four values — minimums for protein and fat, maximums for fiber and moisture — and doesn’t require manufacturers to guarantee an exact percentage, only a floor or ceiling. Dry matter conversion works with whatever numbers are printed, but it can’t correct for that built-in imprecision.

Why does this matter for comparison shopping? Because canned and pouch foods typically contain roughly 75–80% water, while dry kibble contains only about 10%. A can of food listing “8% protein” and a bag of kibble listing “24% protein” are not actually four times as different in protein content as those numbers suggest — a large part of that gap is simply water dilution in the canned product.

Why Moisture Changes Pet Food Comparisons

Picture two foods with the same underlying protein content, one canned and one dry. Because the canned version is mostly water, its protein percentage gets “diluted” on the label. The dry version, with far less water, shows a much higher protein percentage for what could be a similar actual amount of protein once you remove water from both sides of the comparison. Comparing the two labels directly, without adjusting for moisture, is a bit like comparing the sugar content of orange juice to orange juice concentrate without accounting for the added water — the numbers alone don’t tell the full story.

How to Calculate Dry Matter Basis

The conversion is a two-step calculation, consistent with standard veterinary nutrition references (see Sources below):

• Step 1 – Find the dry matter percentage: Dry Matter % = 100 − Moisture %
• Step 2 – Convert a nutrient to dry matter basis: Nutrient DMB % = (As-Fed Nutrient % ÷ Dry Matter %) × 100

Apply Step 2 separately to each nutrient you want to convert — protein, fat, fiber, or others — using the same dry matter percentage from Step 1.

Dry Matter Calculation Example

You can run this calculation for your own pet’s food with the Pet Food Dry Matter Calculator, which does this math automatically for protein, fat, fiber, ash, and an optional carbohydrate estimate.

Wet Food vs Dry Food: Example Comparison

Here’s how label (as-fed) percentages can compare to dry-matter-basis percentages for two hypothetical cat foods:

Read as printed, the dry food looks far higher in protein (30% vs 10%). Once moisture is removed from both, the wet food actually has the higher protein concentration. This does not mean the wet food is automatically the “better” choice — it means the fair, water-adjusted comparison tells a different story than the as-fed numbers alone. Choosing between them still depends on your pet’s individual needs, the food’s overall nutrient profile, and your veterinarian’s guidance.

Dry Matter Basis for Dog Food

For dogs, dry matter comparisons are most often used when comparing a canned or fresh/raw diet against a kibble diet, or when comparing two kibble brands with slightly different label formats. Because commercial dry dog foods vary widely in moisture (roughly 6–12%) and canned dog foods even more so in protein and fat sourcing, converting to dry matter basis is a useful first step before looking more closely at ingredient quality or consulting your veterinarian about a specific product.

Dry Matter Basis for Cat Food

Dry matter comparisons are especially common in cat nutrition discussions, since cats are frequently fed a mix of wet and dry food, and wet cat food in particular can run very high in moisture (often 75–85%). A cat food’s dry-matter protein or fat percentage is generally a more meaningful figure than its as-fed percentage when comparing formats, though as with dogs, it’s only one part of evaluating whether a food is appropriate for an individual cat.

Protein on a Dry Matter Basis

Protein is the nutrient most commonly compared this way, since protein levels are a frequent talking point in pet food marketing. Because wet foods almost always show lower as-fed protein percentages than dry foods purely due to water content, dry matter conversion is particularly important whenever protein is the nutrient being compared across formats. A higher dry-matter protein percentage indicates a higher protein concentration, not necessarily better protein quality, amino acid completeness, or digestibility.

Fat on a Dry Matter Basis

The same logic applies to fat. Wet food will typically show a lower as-fed fat percentage than dry food, again mostly due to water dilution rather than an actual difference in fat content. Comparing dry-matter fat percentages gives a clearer sense of relative fat concentration, which can be relevant context when discussing calorie density or weight management with your veterinarian.

What About Carbohydrates?

Most pet food labels don’t print a carbohydrate percentage directly. It can be estimated using a method called “carbohydrate by difference” (also called nitrogen-free extract, or NFE): 100% minus moisture, protein, fat, fiber, and ash. This requires knowing the ash percentage — if it isn’t printed on the label, the honest approach is to leave the carbohydrate figure as an unknown rather than assume a value for ash that wasn’t actually measured.

Even when calculated, this is an estimate, not a laboratory-measured value. The by-difference method lumps true digestible carbohydrate together with soluble fiber and any rounding or measurement variation from the other guaranteed-analysis numbers, so it can overstate true digestible carbohydrate, particularly in foods high in soluble fiber.

As-Fed vs Dry Matter Basis

As-fed is the percentage exactly as printed on the label, including that food’s own water content. Dry matter basis recalculates that percentage as a share of the food once water is removed. As-fed numbers are only meaningful for comparing foods with similar moisture content (two dry kibbles, for instance); dry matter basis is what allows a fair comparison between foods with different moisture levels, such as wet versus dry.

What Dry Matter Analysis Cannot Tell You

Dry matter basis is a useful comparison tool, but it has real limits. It does not tell you:

• Whether a food is “complete and balanced” for a particular life stage
• Overall ingredient quality or sourcing
• Digestibility — how much of that nutrient your pet actually absorbs
• Calorie density — two foods with identical dry-matter protein percentages can have very different calories per cup or per can
• Nutrient bioavailability or amino acid/fatty acid profile
• Whether the food is suitable for your individual pet, including any medical condition

On that calorie-density point specifically: veterinary nutritionists at Tufts University’s Cummings School note that comparing nutrients per 100 calories can be an even more precise method than dry matter basis alone, since dry matter percentages don’t account for how calorie-dense a food is — two foods can have the same dry-matter protein percentage but deliver very different amounts of protein per meal if their calorie densities differ. Dry matter basis remains a useful, widely used starting point for removing the moisture variable from a comparison; it’s simply not the final word on food quality or suitability.

Common Mistakes When Comparing Pet Foods

• Comparing as-fed percentages directly between wet and dry foods. This is the most common and most misleading mistake.
• Assuming a higher dry-matter number always means “better.” Concentration is not the same as quality, digestibility, or suitability.
• Treating an estimated carbohydrate-by-difference value as a precise lab measurement. It’s a calculated estimate with known limitations.
• Ignoring calorie density. Two foods with similar dry-matter percentages can differ substantially in calories per serving.
• Switching foods based on a dry-matter comparison alone. Diet changes, especially for pets with health conditions, should involve your veterinarian.

How to Use PawCalcHub’s Dry Matter Calculator

Find the “Guaranteed Analysis” panel on your pet food’s label, then enter the Moisture % into the calculator (the only required field), along with any of Crude Protein, Crude Fat, Crude Fiber, Ash, or Carbohydrate percentages you want converted. You don’t need every value — the tool only shows results for the nutrients you actually enter.

When to Talk to Your Veterinarian

This article and the calculator it supports are educational tools, not a substitute for professional veterinary or veterinary-nutrition guidance. Dry matter comparisons can help you understand pet food labels more clearly, but they cannot diagnose a nutritional deficiency, confirm whether a food is complete and balanced, or tell you whether a specific product is right for your individual pet. If your pet has a medical condition, is on a therapeutic or prescription diet, or you’re considering a significant diet change, talk to your veterinarian or a board-certified veterinary nutritionist before deciding based on label comparisons alone.

Related: Pet Food Analysis Tools · Dog Food Calculator · Cat Food Calculator