One of the ways you can check the protein concentration of a product is to do a simple calculation of the grams of protein per serving divided by the total grams per serving. The product should have at least 80% of protein per serving to be considered a decent protein shake. For example, in a 25 gram serving, if the label states that there are 23 grams of protein, the concentration of protein is
23 grams / 25 grams = 92%
This example can be considered a very high-concentration whey protein product (probably a whey protein isolate).
If you want to check the overall quality of a whey protein powder there may be some other things to consider. Check out my article on whey protein here.
Keep growing and stay healthy!