I have no idea what [type of pancake][1] you're making, but I had [answered your question for chemically leavened pancakes][2] in case someone stumbled upon that question (even though the earlier question was specifically for crêpe like pancakes.)


> If you're using baking soda as a
> leavening, it'll have already given
> its all by the time you cook it hours
> later ... but you'd have to add baking
> powder to compensate when it's time,
> as there might not be enough acid left
> for baking soda. Baking powder in the
> batter isn't as much of a problem if
> it's double-acting, where it'll give
> some leavening when it gets wet, and
> again as it gets warm. Of course, you
> don't want to add too much baking
> powder, as it can give a metallic
> taste.

It's also worth mentioning that it *is* possible to [halve an egg][3]; in this case, if you're going to be using the other half of the mix in a day or two, it might be easier to measure by mixing all of the wet ingredients together and then use half.


  [1]: https://cooking.stackexchange.com/questions/13102/how-many-different-varieties-of-pancake-are-there
  [2]: https://cooking.stackexchange.com/questions/12933/given-i-have-to-make-the-batter-now-to-eat-in-3-4hrs-whats-the-best-way-to-stor/12936#12936
  [3]: https://cooking.stackexchange.com/questions/1610/how-do-you-halve-a-recipe-that-calls-for-1-egg