How many Christmas lights you need for a 6ft tree depends on your preference. Some people may prefer to have more lights to create a brighter and more festive look, while others may prefer a more subtle and understated appearance. It's generally recommended to use around 500-800 lights for a 6ft tree, but this can vary based on the type and size of lights you choose. It's also important to make sure that the lights you use are designed for indoor use and are rated for the amount of power your tree will need.