It depends on your preferences, but the size of a Christmas tree is usually measured in feet or meters. For a small space, a 3-4 foot tree is ideal, while a 6-7 foot tree is perfect for a medium-sized room. If you have a large space or want a dramatic look, a 10-12 foot tree will make a stunning statement. Ultimately, the size of your tree should be determined by the amount of space available and your own style preferences.