Most dog food companies list the nutrient content by Guaranteed analysis basis. This method factors in the moisture content, which needs to be factored out  when comparing nutrients between two different brands with different moisture levels

Note: Both the Dry Matter basis and Guaranteed analysis basis are important. One allows you to better compare nutrient content by percentage, the other tells you how much water and absolute amount of nutrients you are buying. See this article for more details. 

Fortunately, most dry dog foods contain around 10%  to 12% moisture content only. This low variance does not change the final nutrient figure a drastic amount. For wet dog food, the variance is higher, which makes the dry matter analysis more useful.

Dry matter basis strips away all moisture in the calculation. Thus , dry matter basis is a true method to perform a fair side by side comparison for nutrient content by percentage in the dry material. However, you still need to consider how much dry matter is left after you remove the moisture.

Here is an example of factoring out the moisture in an Guaranteed analysis basis by converting it to the Dry matter basis  for comparison purposes:

Brand 1: 

• 10% Moisture
• 30% Protein

Brand 2:

• 12% Moisture
• 30% Protein

Remove out moisture with the following equation:

(100% – %Moisture) = %TotalDryMatter

(%Protien / %TotalDryMatter) * 100% = %ProtienWithoutMoisture

Let’s apply it to the two example brands:

Brand 1: (30%/90%) * 100% = 33%  %ProtienWithoutMoisture

Brand 2: (30%/88%) * 100% = 34% %ProtienWithoutMoisture

Results: The true difference is 1%