Nepal has a total population of 27,676,547 as of July 2005, with a growth rate of 2.2%. 39% of the population is up to 14 years old, 57.3% are aged between 15 and 64, and 3.7% above 65. The median age is 20.07 (19.91 for males and 20.24 for females). There are 1,060 males for every 1,000 females. Life expectancy is 59.8 years (60.9 for males and 59.5 for females). Total literacy rate is 53.74% (68.51% for males and 42.49% for females).

According to the 2001 census, Hindus constitute 80.6% of the population. Buddhists make up 10.7%, Muslims 4.2%, Kirant 3.6%, other religions 0.9%. The largest ethnic group is the Chhettri (15.5%). Other groups are the Brahman-Hill 12.5%, Magar 7%, Tharu 6.6%, Tamang 5.5%, Newar 5.4%, Kami 3.9%, Yadav 3.9%, other 32.7%, unspecified 2.8%. Nepali is the national language with 47.8% of the population speaking it as their first language. Other languages include Maithili 12.1%, Bhojpuri 7.4%, Tharu (Dagaura/Rana) 5.8%, Tamang 5.1%, Nepal Bhasa 3.6%, Magar 3.3%, Awadhi 2.4%, other 10%, unspecified 2.5%. Differences between Hindus and Buddhists have been in general very subtle and academic in nature due to the intermingling of Hindu and Buddhist beliefs. Both share common temples and worship common deities and many of Nepal's Hindus could also be regarded as Buddhists. Buddhists are mostly concentrated in the eastern regions and the central Terrai. Buddhism was relatively more common among the Newar and Tibeto-Nepalese groups. Among the Tibeto-Nepalese, those most influenced by Hinduism were the Magar, Sunwar, Limbu and Rai peoples. Hindu influence is less prominent among the Gurung, Bhutia, and Thakali groups, who employ Buddhist monks for their religious ceremonies.

The northern mountains are sparsely populated. A majority of the population live in the central highlands despite the migration of a significant section of the population to the fertile Terrai belt in recent years. Kathmandu, with a population of 800,000, is the largest city in the country.