It is known as "Coca-Cola" route, Marangu approaches Kilimanjaro from the southeast of the Mountain. It is the oldest established route. Many favor the Marangu route because it is considered to be the easiest route on the mountain. The minimum days required for this route is five, although the probability of successfully reaching the top in that time is a bit low. Spending an extra acclimatization day on the mountain is highly recommended, maximizing the chance of reaching to the summit. Marangu is the only route which offers sleeping huts in dormitory style accommodations.
Machame route, also known as the Whisky route, has become very popular. This is camping route which offers spectacular views of various landscapes such as Mt Meru, Pare Mountains, Lake Chala and Lake Jipe. While the 6 day itinerary is very possible, it is very benefitable to have the seven days machame climb because of having one more extra day for acclimatization and resting before the summit day. Doing this will maximize your chance of reaching the top.