Probably a stupid question -- how do I measure how much buttercream I need? Is there some magical mathematic equation? I always feel like I mix it, run out, mix more, run out... How do you determine how much to make in advance? THANKS!!
AThe Cake Bible contains an excellent chart.
You never make just the right amount, no one does. You make whatever the recipe yields....you guess how much. With practice you start to get a feel for how much you need in relation to how big your cake is.
I always deliberately make too much, I want left overs because if I ever have to make touch ups the color will match. And NO one wants to decorate 3/4's of a cake and run out of frosting, than have to make more.
Just make more and be happy for left-overs.
Wilton has a good chart for figuring out how much you will need. I think the last column on right shows how much you need for various size pans.
Now the problem is figuring out how much frosting a recipe makes. I agree with others here to make more than needed. I freeze any leftovers and use for decorations, etc.
I just always make extra. If you think you need two batches, make 3. You can freeze the leftovers in a ziploc bag. When you need it for something like cupcakes, it's ready! I just take it out and leave it on the counter until it comes to room temperature, put back in my stand mixer and whip it.
I wouldn't recommend keeping it too long in the freezer. A few weeks to a month at best. Any longer than that, I think it may taste funky.