The answer to this question is highly dependent upon the distance in which you intend to shoot. Most indoor ranges are at least 20 yards long. If this is the distance at which you would like to shoot, then you would base your plans off this figure. If you are seeking to construct your indoor archery range, you will want to build your structure at a minimum length of five yards longer than your desired shooting distance. This allows you to draw and shoot your bow with correct form without being situated directly against the wall at one end.