Trekking difficulty in Nepal are based on Grade levels from Grade 1 to 4.
Grade 1 [Easy]: These treks do not require you to have prior trekking experience. These treks are also very convenient for old and young making these treks a hit with the family and beginners.
Ghorepani Poon Hill, Everest short trek, Around Kathmandu valley trekking are good examples.
Grade 2 [Moderate]: These treks can be done by beginners but do require you to be at least moderately fit with some regular exercises. The average altitude of these treks will be 3900 meters to 4800 meters and does cover some steep passes occasionally.
Annapurna base camp, Langtang valley trek & Gokyo lake Everest trek are some examples of moderate level trekking.
Grade 3 [Strenuous]: These trekking routes do require you to be physically fit, good stamina and a person with regular exercise habit. You will walk for about 6 hours daily on average and generally the altitude will be above 4800 meters to 5600 meters. Accommodation too will not be good enough in comparison to other regular trekking trails.
Everest base camp, Annapurna circuit, Upper Mustang trek, Guerrilla Trail are some good examples of strenuous trekking in Nepal.
Grade 4 [Challenging/Alpine trekking]: This trek constantly challenges you with many trek across high passes, snow glaciers and icy path. Previous trekking experiences are of utmost importance if you want to get through with this trek.
Make sure to check with your Tour agency and website on the level of difficulty of your trekking destination.
The challenging treks in Nepal are:
Three Passes Trek: This very challenging trek crosses three passes of over 5,000 metres – Kongma La (5,535 metres), Cho La (5,420 metres) and Renjo La (5,340 metres).
Dhaulagiri Circuit: This challenging trek is a camping trek meaning no lodges are used for accommodation.And this trek covers requires you to spend three days in a row trekking above 5,000 metres.
Upper Dolpo Trek: This is one of the most remote and hard-to-reach places in the country. The infrastructure for trekkers is practically non-existent, so you’ll need to carry in all of your food and equipment, including tents.
Kanchenjunga Trek: This trek requires you to walk on an average of 5 days for 27 days, making it one of the longest and demanding treks you will encounter in Nepal.