Ideal number of days to spend in Nepal:
Although a small country, Nepal has much to offer. Yes, Nepal is famous for towering mountains. But we also have a diverse culture, numerous historical and religious sites, jungles with wildlife and other natural beauty. It is the perfect destinations for extreme mountaineers, casual hikers and non-hikers alike. In our opinion, for non-hikers, a minimum of 9 days is required to explore and understand Nepal. If you come for a shorter period, you will only be able to explore the Kathmandu valley and the surrounds such as Nagarkot or Dhulikhel. Past visitors to Nepal will concur that Kathmandu does NOT represent Nepal and the real Nepal lies outside of the bustling capital. Coming for at least 9 days will allow you to travel to Pokhara and Chitwan besides just Kathmandu.
For hikers too, a minimum of 9 days in Nepal is required. After exploring Kathmandu, you would travel to Pokhara for a short trek in the foothills of the Annapurna range. Below are some options based on how many days you decide to spend in Nepal:
5 days in Nepal

If you travel to Nepal, you must come for at least 5 days. It’s best not to travel to Nepal if you are traveling for fewer than 5 days unless you are also traveling to India, Bhutan and/or Tibet. In 5 days, you could explore seven of the World Heritage Sites in the three ancient cities of Kathmandu (over two days), spend a night at Nagarkot or Dhulikhel or the newly opened luxury resort at Lakhuri Bhanjyang to view the mountains and to take a short hike for an experience of hiking in Nepal.
Below is a suggested 5-day itinerary:
Day 01: Arrive in Kathmandu.
Day 02: Sightseeing of Patan City and Bodhnath.
Day 03: Sightseeing of Pashupatinath and Bhaktapur Durbar Square. Continue to Nagarkot or Dhulikhel or Lakhuri Bhanjyang. Overnight.
Day 04: Hiking in the morning. You may opt to spend a second night here or return to Kathmandu.
Day 05: Final departure.
7 – 9 days in Nepal

A week or more in Nepal allows you enough to time to include Pokhara and view the majestic Annapurna mountains up-close. In the above itinerary, you would forego Nagarkot/Dhulikhel and instead fly to Pokhara for two/three nights. You can also add a short trek 1-2 day trek in the foot-hills of Annapurna.
7-day non-trekking journey in Nepal:
Day 01: Arrive in Kathmandu.
Day 02: Sightseeing of Patan City and Bodhnath.
Day 03: Sightseeing of Pashupatinath and Bhaktapur Durbar Square.
Day 04: Fly to Pokhara. Boat ride across the Fewa lake. Hike to the Peace Stupa.
Day 05: Drive to Sarangkot/Kaskikot for views of the Annapurna and Dhaulari ranges. Visit International Mountain Museum.
Day 06: Fly to Kathmandu.
Day 07: Final departure
If you add two more days, you could also visit the jungles of Chitwan in Nepal. Here, you are guaranteed to see the one-horned rhinoceros and the gharial or mugger crocodiles. But you’d have to be very lucky to spot the elusive Royal Bengal Tiger. Check out our 9-day Nepal tour: A non-trekking Journey to Nepal.

9-day short-trek journey in Nepal:
Day 01: Arrive in Kathmandu.
Day 02: Sightseeing of Patan City and Bodhnath.
Day 03: Sightseeing of Pashupatinath and Bhaktapur Durbar Square.
Day 04: Fly to Pokhara. Drive to Ghandruk.
Day 05: Trek to Tadapani.
Day 06: Trek to Ghorepani
Day 07: Hike to Pun hill and descend to Ulleri. Drive back to Pokhara
Day 08: Fly to Kathmandu.
Day 09: Final departure
Check out our slightly longer 12-day Annapurna Skyline Trek program. It is possible to cut out some trek days if you don’t have that much time.
10 days to 2 weeks in Nepal:

With more than 10 days, more options open up. In the Annapurna region, if you wish to avoid the popular Ghorepani route, you could trek to the Khopra Ridge.
You can also now trek to places besides just the Annapurna region. This includes to Pikey Peak in the eastern part of Nepal in the lower Everest region. You could even do a relaxed pace Tengboche Monastery trek in the Khumbu region for up-close views of Mt Everest. Or to the Langtang Valley. The combined Langtang and Gosaikunda Treks are slightly longer (15 days) but you could choose to do just the Langtang Trek or the Gosaikunda Trek.
If you are an avid mountain biker, the biking in the Kali Gandaki Valley in Lower Mustang is considered one of the best. Check out our 12-day Mountain Biking in Nepal program.
If you are not interested in a trek, with two weeks you can explore more of Nepal. You could travel to Lumbini – the birth-place of Lord Buddha. You could also travel west to Bardia National Park where tiger sightings are more common than in Chitwan National Park.
Upto 3 weeks in Nepal
For avid trekkers, we highly recommend 15+ days in Nepal. This allows you choose from several options including:
In the Everest region, your options open up including the iconic trek to Everest Base Camp. We have two options of this trek: the 15-day fast-paced EBC trek and the standard 19-day Everest Base Camp Trek which allows more time for acclimatization.
You could also forego the popular EBC trek route and instead embark on our 18-day Gokyo Valley Trek. We have also started operating trail-running treks and you could choose our 18-day Ultimate Everest Running Trek that first visits the Everest Base Camp and then goes over the Cho La pass to Gokyo Valley. It then continues over the Renjo La pass to the Thame valley. Besides the Everest region, you could also circle the Manaslu massif on our 18-day Manaslu Circuit Trek.
Another popular trek is the 15-day trek to the Annapurna Base Camp. Or the 16-day Annapurna Circuit Trek. Mountain bikers can choose to do the 15-day Annapurna Circuit on a mountain bike.
There are also several options in the Upper Mustang region. This region falls in the rain-shadow of the Himalayas and is not the alpine terrain one envisions when they think of Nepal. Instead it is a high-desert. We have a 17-day fast-paced Upper Mustang Trek and a standard 20-day Upper Mustang Trek. You could also do this trek on a mountain bike on our Biking Upper Mustang program.

If you like trekking in a remote region and like tents instead of lodges, you would love the 19-day Dhaulagiri Circuit Trek. This trek circles the Dhaulagiri massif and involves crossing the French pass which takes you to the hidden valley. One of my all-time favorite treks.
4 Weeks or more in Nepal
Four weeks in Nepal really allows you to explore the most remote parts of Nepal. This includes a camping trek to 35 day Upper Dolpo Trek.

Other longer treks to remote regions of Nepal include the 27-day Kanchenjunga Base Camp Trek (Or the slightly shorter 24- day lodge trek to Kanchenjunga Base camp). Another lodge trek option is the 23-day Makalu Base Camp Trek. In the Everest region, your options for a long trek include the 23-day Ultimate Everest trek or the 24 day Three passes Trek. You could also climb a trekking peak including the 23-day Island Peak, Lobuche Peak or Mera Peak. Participation in climbing these peaks require basic mountaineering skills such as use of crampons, ice-axe, ice-axe arrest skills etc.