The guaranteed analysis lists nutrient percentages "as fed," meaning water is counted in the total. Dry matter basis strips the water out so foods with different moisture levels can be compared honestly. The conversion is one line of arithmetic: divide the as-fed percentage by (100 minus the moisture percentage), then multiply by 100.
Why does moisture wreck the comparison?
Because water dilutes every other number on the panel, and moisture varies enormously between food types. Dry kibble runs about 10 percent water. Canned food runs 75 to 82 percent. Gently cooked fresh food usually lands between 65 and 75 percent.
So when a kibble bag guarantees 26 percent protein and a fresh food package guarantees 11 percent, the kibble looks like it has more than twice the protein. It doesn't. Most of what's in the fresh package is water, and water isn't protein or anything else. Compare the labels as printed and you'll reach the wrong conclusion every time.
How do you convert to dry matter?
Work the formula on one nutrient at a time.
Dry matter % = (as-fed % ÷ (100 − moisture %)) × 100
Take that fresh food at 11 percent protein and 72 percent moisture. Its dry matter content is 100 − 72 = 28 percent. So: 11 ÷ 28 = 0.393, times 100 = 39.3 percent protein on a dry matter basis.
Now the kibble at 26 percent protein and 10 percent moisture. Dry matter is 90 percent. So: 26 ÷ 90 = 0.289, times 100 = 28.9 percent protein.
The fresh food has substantially more protein per unit of actual food. Reversed from what the panel appeared to say.
What does a full comparison look like?
Every number shifts, and the fat gap widens more than the protein gap. This is the whole reason nutritionists never quote as-fed figures when comparing across formats. Run the conversion once for each food you're considering and keep the results in your phone's notes app. A recipe like Chicken & Beef reads very differently after the arithmetic than before it.
What do "minimum" and "maximum" really mean?
They mean the guarantee is a boundary, not a measurement. "Crude protein, min 9%" promises the food contains at least 9 percent. The actual batch might contain 12. Fat and protein carry minimums; moisture and fiber carry maximums.
This introduces slack into every comparison you make. Two foods both guaranteeing a 9 percent minimum could differ by three or four percentage points in reality. If precision matters — a weight management plan, a dog on a restricted diet — call the manufacturer and ask for a typical nutrient analysis, which reports what the food actually tests at rather than what's promised.
Where does "crude" come from?
It refers to the laboratory method, not the quality of the ingredient. Crude protein is calculated by measuring nitrogen and multiplying by 6.25, since most proteins are roughly 16 percent nitrogen. That works fine for real meat. It also means any nitrogen-containing compound registers as protein, which is precisely how the 2007 melamine adulteration passed testing. Reputable manufacturers run amino acid assays beyond the crude number for exactly this reason.
When are calories the better yardstick?
Whenever you're deciding how much to feed rather than what to buy. Percentages describe composition; calories describe how much food goes in the bowl.
Labels list metabolizable energy as kcal per kilogram and usually kcal per cup or per package. That second number is the one you use daily. A fresh recipe at roughly 1,250 kcal/kg means a 400-gram package delivers about 500 calories — enough for a moderately active 30-pound dog for a full day. Dry matter percentages won't tell you that; only the calorie figure will. For working through your dog's daily number, our portion guide walks through the equation.
What does the guaranteed analysis leave out entirely?
A surprising amount:
- Carbohydrate content, which is never listed and must be estimated by subtraction: 100 minus protein, fat, moisture, fiber, and ash
- Which amino acids make up that protein, so a food heavy in connective tissue can post the same protein number as one built on muscle meat
- Fiber type — crude fiber captures insoluble fiber well and soluble fiber poorly, so a pumpkin-rich recipe may read low despite meaningful fiber content
- Digestibility, meaning how much of any of it your dog actually absorbs
- Omega-3 to omega-6 ratio, unless the maker voluntarily adds it
The panel is a floor and a ceiling, not a portrait. Tufts' Petfoodology is a reliable place to read further on where the gaps are.
How do you compare two foods in five minutes?
- Write down moisture, protein, fat, and fiber for both, straight off the panels.
- Convert each nutrient to dry matter using the formula above.
- Note kcal per kilogram for both.
- Estimate carbohydrate by subtraction if it matters to you.
- Compare cost per 1,000 calories rather than cost per pound, since a wet food's water weight inflates the price per pound.
That last step reframes the value question honestly. And before you switch foods based on a spreadsheet, run the final numbers past your dog's clinic — bloodwork and body condition tell you things a label comparison never will. Our overview of fresh food versus kibble covers the practical side of that decision.
FAQ
Do I need to convert to dry matter when comparing two dry kibbles?
Not really. Both will sit near 10 percent moisture, so the conversion shifts both numbers by nearly the same factor and the ranking doesn't change. The conversion earns its keep when moisture levels differ by more than about 10 percentage points, which happens whenever you compare across formats.
How do I find carbohydrate content if it isn't listed?
Subtract protein, fat, moisture, fiber, and ash from 100. Ash usually isn't guaranteed either, so assume 6 to 8 percent for most foods, or call the manufacturer. The result is called nitrogen-free extract and it's an estimate, not a precise figure.
Is higher protein on a dry matter basis always better?
No. Adult dogs at maintenance do well across a wide protein range, and more isn't automatically an improvement. Amino acid profile and digestibility matter more than the raw percentage, and dogs with certain kidney or liver conditions need protein deliberately moderated under veterinary direction.
Why does fresh food cost more per pound if it's mostly water?
Per pound is the wrong unit, which is why cost per 1,000 calories is the fairer comparison. Fresh food is still usually more expensive that way, because refrigerated shipping, human-grade ingredients, and gentle cooking all cost more than extrusion. The gap is just narrower than the shelf price suggests.
Can I use dry matter numbers to compare a food to AAFCO minimums?
Yes, and you should — AAFCO nutrient profiles are published on a dry matter basis. Convert the label's as-fed figures first, then compare. Doing it the other way around makes wet foods look deficient when they aren't.