M.R.
I always froze 5-6 ounces in a bag since that is the capacity and my boys were voracious. Thaw one bag and then thaw a second for now if the first is not enough--hold it under cool to warm (not hot) running water to thaw it a little faster so you can see if you need more. If you can get an idea from thawing one how much is in it, you can use it to guess how much is in all the other bags or containers. I always highly recommend Lansinoh bags and The First Years milk storage container for the freezer--keeps everything compact and organized and the bags are great.