I bought medium eggs by accident and I don't really want to buy an new carton until these are gone. I know recipes are usually based on large eggs. So my question is...Should I use an extra egg or will it be ok with the amount called for in the recipe? Thanks for any advice you can give. This site is so helpful.
If you have a food scale, I would weigh them.
A large egg is 1.75 oz. If 2 large eggs weighs 3.5 oz, then you can add the amount of medium egg that will add up to that amount.
I don't know how much a medium egg weighs. But if you Google weight of medium egg or equivalent amount of medium to large eggs you will probably get a faster answer.
Google is your friend, even in baking. 
It might go without saying, but it really depends on what type of recipe, and how many eggs it calls for. Sure, you can weigh them, and make up any missing egg, but if the recipe only calls for a couple eggs, any difference is going to be pretty minuscule, and irrelevant unless eggs a main/crucial ingredient.
Weight is a great trick to know though! I've used it many times. 
Quote by @%username% on %date%
%body%