For some climbers (so-called sky-runners) it is a matter of several hours to get to the top and back. Karl Egloff ran up Kilimanjaro in 6 hours and 42 minutes and is the world record holder for speed. Not only is Karl a professional athlete, but he also spent time acclimatizing to the high altitude before starting his speedy ascent.
The average person should consider trips with 7 and longer days to acclimate better. 5 and 6-day programs should be normally avoided (unless a climber has a very good fitness level), with the exception of Marangu and Lemosho 6-day programs for the time-constrained climbers.

Mt. Kilimanjaro Climbing Routes - Difficulty Levels

1. Lemosho Route This route is incredibly scenic and considered one of the easier routes because the terrain to reach Barranco Camp is rather flat, making the first day easy. The Lemosho Route has been used by many record-holders for age, including the youngest and oldest record holders.
This route usually is attempted over 7 to 8 days.
2. Machame Route - Sought after because of the beautiful trek through a rainforest on the first day, this trek is one of the most scenic approaches up Kilimanjaro. However, its six-day itinerary is one of the most difficult ones, and we recommend a much simpler 7-day itinerary to help reach Uhuru Peak.
3. Marangu Route This tough route has one of the lowest success rates, especially for climbers on the 5-day itinerary. A 6-day trek is much better overall, even better than its friend, the 6-day Machame Route (but not the 7-day). A draw-back is that his route can be quite crowded during high season. Also, the same trail is used both for ascent and descent.
4. Rongai Route - This is the only route that approaches Kilimanjaro from the north, near the Kenyan border. The 7-day trek poses some challenges but is overall a great climb for acclimatization. It is not recommended to attempt this route in under 7 days.
5. Northern Circuit Route poses an incredible adventure, including crater camping and hiking along a less traveled route. While offering the longest itinerary (8 or 9 days), the scenery around the circuit is incredible and well worth the added days. Also, the longer route provides for excellent acclimatization.
6. Umbwe Route is a very steep ascent and is only suggested for the most experienced climbers. Karl Egloff and other ‘sky runners’ summited Kilimanjaro via this route.