Knowing how to read your dog food label is very important, while the pricing of the food might be a good start to indicate quality its always best to know for yourself. Here's one of many things you can do to be able to compare different food brands:

Converting % to dry matter

Knowing how to convert foods into dry matter (no moisture) is important because it helps you compare crude protein and fat between two brands that might have different moisture levels. Heres the conversion formula:

(moisture% - 100%) = drymatter% ; (protein% / drymatter%) = % of protein on dry matter base

Dry Dog Food Brand: Has 10% moisture and 20% crude protein. Since we subract the 10% moisture from 100% we get 90%, this is simply the percent of dry food (no moisture). Now you take the 20% protein and divide it by the 90% dry matter and you get 22% protein, which is the amount of dry matter on a dry food basis.

Wet Dog Food Brand: Has 80% moisture and 5% protein. If you do the same and subtract 80 from 100 you get 20% dry matter. Now you divide the 5% protein by the 20% dry matter and you get 25% protein on a dry matter basis.

Comparing the two you can see that your dog will get more protein per pound with the wet dog food in this case. You can do this for fat, fiber, etc and for foods that have different moisture percents.

http://peteducation.com/article.cfm?c=2+2099&aid=668

good info! very interesting! *thumbs up!*