Baking may require precision, but that doesn't mean you can't experiment within reason. This holds especially true with two forgiving categories of recipes: quick breads (like banana bread and coffee cake) and muffins. The key nugget to know is that these easy breakfast treats are made from virtually identical batters; where they differ is in the baking vessel used. If you have a solid quick bread recipe that you'd like to convert to muffins, try this.
If you'd like to convert a muffin recipe to a quick bread loaf, try this.