Dry Matter Calculator
Pet food labels print nutrients on an as-fed basis, which includes water. A wet food with 78% moisture and a kibble with 10% moisture look completely different on paper, even if their actual nutrition is similar. This calculator removes the moisture and shows you each nutrient on a dry matter basis, so you can compare any two foods side by side on equal footing. Enter the guaranteed analysis from the label and get the corrected protein, fat, fiber, ash, and carbohydrate percentages instantly.
Formula
Worked example
A wet cat food shows 9% protein and 78% moisture. Dry matter = 100 - 78 = 22%. Protein on DM basis = (9 / 22) x 100 = 40.9%. A dry kibble shows 30% protein and 10% moisture. Dry matter = 90%. Protein DM = (30 / 90) x 100 = 33.3%. So the wet food actually delivers more protein per unit of dry matter despite the lower label figure.
Why as-fed percentages are misleading
When you look at a pet food label, every nutrient percentage includes the water in the food. A can of wet food that is 78% moisture already has less than a quarter of its weight available as actual nutrients. A dry kibble at 10% moisture is much more concentrated. This means a wet food showing 9% protein and a dry food showing 30% protein cannot be compared directly because they contain very different amounts of water. Converting both to a dry matter basis removes the moisture from the equation, leaving you with the percentage of each nutrient per gram of actual food solids. Only then can you make a fair side-by-side comparison.
How to read the guaranteed analysis on a pet food label
The guaranteed analysis (GA) panel on a pet food label lists crude protein (minimum), crude fat (minimum), crude fiber (maximum), and moisture (maximum). These are regulatory floors and ceilings, not exact values. Ash (minerals) and carbohydrates are often not required on the label in the US. If ash is not listed, a common estimate is 6% for dry foods and 2% for wet foods, though the manufacturer can give you the actual figure. Carbohydrates are calculated by subtraction: 100 minus protein, fat, fiber, ash, and moisture. Because the GA values are minimums and maximums rather than actual amounts, the dry matter calculation gives an estimate. Asking the manufacturer for a typical (mean) nutrient analysis gives a more accurate starting point.
Wet food vs. dry food: what the numbers look like after conversion
A typical wet cat food with 9% protein and 78% moisture converts to about 40.9% protein on a dry matter basis. A typical dry kibble with 30% protein and 10% moisture converts to about 33.3% protein DM. So the wet food that looked much lower in protein on the label actually delivers more protein per unit of dry food solids. The same logic applies to fat, fiber, and carbohydrates. This is why veterinary nutritionists always recommend comparing foods on a dry matter basis rather than from the label directly.
Carbohydrates in pet food: why they matter for cats
Unlike dogs, cats are obligate carnivores and have limited metabolic ability to handle high-carbohydrate diets. Cats lack the salivary amylase enzyme that starts carbohydrate digestion in omnivores. Many dry kibbles are high in carbohydrates because starch is needed to bind the pellet shape, and on a dry matter basis these can range from 30-50% or more. Some cats do fine on this, but others are better served by lower-carb wet or raw diets. The carbohydrate estimate in this calculator gives you a starting point for comparing foods, but remember it is derived by subtraction and may not be perfectly accurate without an exact ash figure from the manufacturer.
Typical nutrient ranges for cat and dog food (dry matter basis)
| Nutrient | Cats (AAFCO min) | Dogs (AAFCO min) | Notes |
|---|---|---|---|
| Protein (adult) | 26% DM | 18% DM | Higher in kittens/puppies |
| Fat (adult) | 9% DM | 5.5% DM | Essential for fat-soluble vitamins |
| Fiber | 1-10% DM | 1-10% DM | Varies widely by formula |
| Moisture (wet food) | 70-85% | 70-85% | Aids hydration |
| Moisture (dry food) | 8-12% | 8-12% | Extended shelf life |
| Carbohydrates | Not required | 0-70% | Cats prefer lower carb |
General benchmarks from AAFCO guidelines. Actual needs vary by age, breed, and health status. Consult your vet for individual recommendations.
Frequently asked questions
What is dry matter basis?
Dry matter basis (DMB) is a way of expressing nutrient percentages as if all the water were removed from the food. It lets you compare the actual nutrient content of wet food, dry food, and raw food on equal terms, because the moisture content of these foods varies enormously and otherwise makes direct comparison impossible.
How do I convert an as-fed percentage to dry matter basis?
Subtract the moisture percentage from 100 to get the dry matter percentage. Then divide the as-fed nutrient percentage by the dry matter percentage and multiply by 100. For example: a food with 9% protein and 78% moisture has 22% dry matter. Protein DM = (9 / 22) x 100 = 40.9%.
Where do I find the moisture and protein percentages?
They are printed on the guaranteed analysis panel on the pet food package, usually on the back or side of the bag or can. The label shows crude protein (minimum), crude fat (minimum), crude fiber (maximum), and moisture (maximum). Note that these are regulatory minimums and maximums, so the actual values may differ slightly.
What if ash is not listed on my pet food label?
Ash is not required on US pet food labels, though it is required in the EU. If it is not listed, you can estimate 6% for dry kibble or 2-3% for wet food, or contact the manufacturer for the actual figure. The ash value affects the estimated carbohydrate calculation, so leaving it at 0 when the food does contain ash will cause the carbohydrate estimate to be overstated.
Why does my calculation not add up to 100%?
The guaranteed analysis values are regulatory minimums and maximums, not mean values. Protein and fat are minimums (the actual levels may be higher), while fiber and moisture are maximums (actual levels may be lower). This is why the values on the label often do not add up to 100%, and why your dry matter conversion may look slightly off. For a precise calculation, ask the manufacturer for a typical (mean) guaranteed analysis.
Is a higher protein percentage always better?
Not necessarily. The quality and digestibility of the protein source matters as much as the percentage. A food with 40% dry matter protein from whole meat ingredients may be far more beneficial than one with the same percentage from plant-based or lower-digestibility sources. Always look at the ingredient list alongside the nutrient percentages.