I have been baking long enough to be able to eye the batter and know which pan to use.
I can also easily switch from a cake tin, to a muffin tin, to a loaf pan and just adjust the baking time.
Banana bread is a good example. My kids prefer it baked in muffin cups, Dad has jumbo muffin tins, so I only make 6 instead of 12. The same batter makes one loaf, 12 regular muffins or 6 jumbo ones. I have also bakes it in a cake tin at times.