The Moisture Problem
When you look at a wet food label showing 10% protein and a dry food showing 30% protein, the dry food seems far superior. But this comparison is completely misleading — and it's one of the most common mistakes cat owners make. The culprit? Moisture content.
Wet food is roughly 78% water, while dry food is only about 10% water. You're not comparing protein to protein — you're comparing protein-in-water to protein-without-water.
What Is Dry Matter Basis?
Dry matter basis (DMB) is a simple mathematical conversion that removes water from the equation, letting you compare the actual nutrient concentration of any two foods regardless of their moisture content. Think of it as looking at what's left after you evaporate all the water.
The Formula
Dry Matter % = 100% - Moisture %
Nutrient on DMB = (Nutrient % ÷ Dry Matter %) × 100
It sounds technical, but it's straightforward once you do it a few times.
Worked Example
Let's compare two real-world scenarios:
Wet food: 10% protein, 78% moisture
Dry matter = 100 - 78 = 22%
Protein DMB = (10 ÷ 22) × 100 = 45.5%
Dry food: 32% protein, 10% moisture
Dry matter = 100 - 10 = 90%
Protein DMB = (32 ÷ 90) × 100 = 35.6%
The wet food actually has nearly 10 percentage points more protein on a dry matter basis. The label numbers told the exact opposite story.
This is why so many cat owners unknowingly choose lower-protein food. Dry food labels look impressive at a glance, but wet food often delivers superior nutrition once you account for moisture.
Quick Mental Math Shortcuts
You don't need a calculator every time. Use these approximations:
- For wet food (~78% moisture): multiply the label percentage by 4.5 to estimate DMB
- For dry food (~10% moisture): multiply by 1.1
- For semi-moist food (~35% moisture): multiply by 1.5
So a wet food with 12% protein: 12 × 4.5 ≈ 54% protein DMB. That's excellent.
Apply It to Fat and Fiber Too
Dry matter basis isn't just for protein — use it for any nutrient:
| Nutrient | Wet Food (as-fed) | Wet Food (DMB) | Dry Food (as-fed) | Dry Food (DMB) |
|---|---|---|---|---|
| Protein | 10% | 45% | 32% | 36% |
| Fat | 6% | 27% | 15% | 17% |
| Fiber | 0.5% | 2.3% | 4% | 4.4% |
Why this matters for health conditions: If your vet says your cat needs "low phosphorus" or "high protein," they're talking about dry matter basis values. Comparing as-fed numbers could lead you to choose the wrong food.
Why MealMeow Uses DMB
Our food database and scoring system compares all foods on a dry matter basis automatically. When you browse recommendations or compare products, you're always seeing an apples-to-apples comparison — whether you're looking at a premium pâté or a budget kibble. No mental math required.
Sources
- National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press, 2006. View source
- Case, L.P. et al. Canine and Feline Nutrition: A Resource for Companion Animal Professionals. 3rd ed., Mosby Elsevier, 2011. View source
- AAFCO. Official Publication. Association of American Feed Control Officials, 2024. View source