The ideal number of lights per foot of Christmas tree depends on the size of the tree and personal preference. For a small to medium-sized tree, 100 lights per foot is generally sufficient. For a larger tree, consider using up to 150 lights per foot. If you're looking for more of an extravagant look, you can go up to 200 lights per foot. Ultimately, the key is to achieve a balanced and well-lit look that fits your tree size and personal style.