The size of your Christmas tree skirt depends on the size of your tree. A general rule of thumb is to choose a skirt that is 2 to 3 feet wider than the width of your tree. If your tree is a standard 6-foot tree, then a skirt that's 8 to 10 feet wide should be sufficient. However, if you have a larger tree, you may need to choose a larger skirt. Ultimately, the best size for your tree skirt will depend on your personal preferences and the size of your tree.