When you compare different types of foods—canned, kibble, etc. or simply different brands—you need to keep in mind the moisture content so you can compare like to like. Use the dry-matter basis.
First, establish the amount of dry matter by subtracting the percentage given for moisture from 100 percent. If the moisture is given as 10 percent, the food’s dry-matter content is 90 percent.
Next, convert the protein found in the Guaranteed Analysis statement to a dry-matter basis by dividing its percentage by the amount of dry matter (calculated in the previous step). For example, if the protein is given as 26 percent, it converts to 28 percent on a dry-matter basis (26 divided by 90). If the moisture level had been, say, 30 percent, the dry matter content would have been 70 percent and protein would have been 37 percent (26 divided by 70).
You can do similar calculations for fat and fiber after converting their percentages to a dry-matter basis.