The number of lights for a Christmas tree varies depending on the size of the tree and the desired effect. A smaller tree may only need 100-200 lights, while a larger tree may require 500-1000 lights. For a more dramatic look, some people choose to add colored lights or even light-up ornaments to their trees. Ultimately, it's up to the individual to decide how many lights they want to use, based on their personal taste and the size of their tree.