One egg equals 1/4 cup egg substitute. You can almost always replace substitute with real eggs, but the reverse is not necessarily true.
Some egg substitutes are egg whites with added ingredients for color or texture. It is also possible to buy egg substitute that is both white and yolk‚Äîbut again, it has been processed and will not have all the same culinary properties as a fresh egg. For example, you cannot whip egg substitute for a meringue. For more tips on using eggs in recipes, see 7 Ways with Eggs.