You should take the time to prepare before you go to buy a Christmas tree. You will first have to decide where you would like your tree at. Most people put them in the living room. Once you have found the perfect spot, you can then start measuring. You will want to measure from your ceiling down to the floor. Then take a few inches off that measurement. You will want to leave room for the topper. If you already have a topper, you can take a better measurement. No matter where you go to purchase your tree, they will be organized by size. You will just have to take your measurement and find a tree that will fit.