The length of the rope you need will be dependent on the length of the climb and its characteristics. Because of the limited height of indoor climbing walls most ropes for this purpose don't need to be longer than about 30 meters. Perhaps 40. Outdoor routes however can be considerably longer. In most cases you're going to want at least 50 meters of rope and in many cases more. The last thing you want is to be left short by your rappelling rope. As a general rule, 50 meter ropes will suffice for most rock routes, unless of course you're tackling El Capitan. Even so it's always a good idea to have a little more rope than you think you're going to need. Just in case.\r