Mayonnaise does not make a very good substitution for eggs because of the fact that it contains so much vinegar and oils, although this is not always the case with all recipes. There are certain recipes such as those involving chocolate cake where it is acceptable to use mayonnaise instead of eggs.
It will be important to use one cup of mayonnaise for every three eggs which are required. You will also want to consider that you will want to add a Â½ cup of mayonnaise for every 2 cups of flour in a recipe. It is important to keep in mind that typically mayonnaise does not make a good substitute for eggs because it throws off the taste, though there are certain recipes where doing so is acceptable.