Welcome to the Cake Decorators Q&A
Can you use a 3" cake belt on a 1.5" cake tin?
I don’t see why not. The belt will be a lot taller than the cake tin but it should still give the same protection for the cake. If you’re not completely happy about using the taller belt, it’s easy to create a home made one to fit the size of your own tin. If you google‘how to make a cake belt’, you’ll find several tutorials.
I hope suggestion helps. 🙂