My muffin recipe calls for 1 1/3 cups of nonfat dry milk. Other than the 4 eggs, there is no other liquid. How much skim milk would I substitute for the dry milk?
You don't, it will not work.
You want to substitute liquid milk for dried milk.
What you don't realise is that the dried milk in such a recipe is acting as a bulking agent, ie. the dried milk is already substituting for some flour.
If you don't have dried milk, you should look for another recipe that doesn't use it, if you want to be certain of reliable results.
I have to respectfully dissagree with the above post. 2 cups of water and 1 cup of dry milk gives you 2 cups if milk... it does not add to the bulk. You can however, substitute scalded milk for powdered milk. Powedered milk is called for generalky when regular milk enzymes will react with your ingredients and make an inferior product, especialky in bread making. Scalding the milk removes the enzymes.