The amount of ribbon needed for a Christmas tree varies depending on its size. A small tree may require about 10 to 20 feet of ribbon, while a large tree may require 50 to 70 feet or more. It's best to measure the height and circumference of the tree and then add a few extra feet for good measure. Be sure to cut the ribbon into sections that are long enough to wrap around the tree several times and still allow for some extra length for tying and decorating.