I am making a car cake and need about 20 servings. I am planning on stacking three 9x13s and then carving them down. Do you think that will be about right? I have no problem with servings for normal cakes but I am having a hard time visualizing the end size. Thanks

I'd say you are right on with that amount.

I depends on how tall they are. A 1/4 sheet will serve about 20. I use a 12" square cut in half and stacked. Maybe an extra 6" for scraps if the roof isn't quite tall enough.

Was trying to attach a photo but it won't do it...