An attempt to conduct a population census in 1979 could not be completed because war broke out. The official population number from Statistics Afghanistan in Kabul (27 million people) is based on an estimated population increase of 2.6% based on the information the then government claimed that it had presented in 1979.
The official population figures do not take into account the immense diaspora and internal displacement in 1980-90 (about half the population), or the return of 5.5 million people from neighbouring countries and the dramatic rate of urbanisation in the 2000s.
There is considerable seasonal labour migration of men to the cities during the summer months, as well as temporary labour migration, mainly to Iran and the Arabian Peninsula and to some extent Pakistan, which further complicates the calculation of the total population, as well as the actual population in various parts of the country.
It is estimated that about 70% of the population live in rural areas. The major cities are the capital Kabul, Mazar-i-Sharif and Kunduz in the north, Herat in the west, Kandahar in the south and Jalalabad in the east.
The country is most densely populated in the provinces around the capital, Kabul. Other densely populated areas are mainly in the Herat area, in the west, the plains around Kunduz in the north and Nangahar Province to the east and along the rivers in the provinces of Kandahar and Helmand in the south. The resident rural population lives mostly in small villages adjacent to rivers and irrigated areas.
There are some 10 larger and more than 30 smaller ethnic groups.
The largest ethnic group is the Pashtun. Most Pashtun live in the southern and eastern parts of the country. There are also large groups of Pashtun in northern and western Afghanistan. The number of Pashtun is estimated at 45% of the population.
Most Pashtun speak Pashto which is a language from eastern Iran.
The second largest ethnic group is the Tajik who constitute about 25% of the population. They live mainly in the north and northeast and in cities. In the west, in Herat province, there is a large Tajik population often called Farsiwan. Most Tajiks speak Dari (Afghan Persian), except in the west where they speak Farsi (Iranian Farsi).
Several Turkish peoples such as Uzbeks and Turkmens live in northern Afghanistan. Uzbeks, who make up about 15% of the population, speak either Dari or Uzbek, a Turkic language. The Turkmen speak the Turkish language Turkmen and/or Dari. There are approximately 500 000 Turkmen in Afghanistan.
There are also Dari-speaking Arabs in northern Afghanistan. Small groups of Arabs also live in eastern Afghanistan.
The Hazara live largely in Hazarajat in the central highlands, as well as in cities such as Kabul, Mazar-i-Sharif (in northern Afghanistan) and in Herat where they form a significant immigrant population. Small groups of Hazara live in other parts of the country.
Hazara are of Mongolian descent. In contrast to most other groups most Hazara are Shia Muslims. An estimated 15% of the population are Hazaras who speak Hazaragi, a Persian dialect, but most also speak Dari.
Far to the northeast, in the Wakhan Corridor, lives a small group of Kirghiz (a Turkic people) and Pamir (a Dardic people).
Far to the south and the west, live the Baluchi and some Brahui. The Baluchi speak Balochi (an Iranian language) and the Brahui speak Brahui (a Dravidian language).
In western Afghanistan, the four Chahar Aimak peoples - Kala Nao Hazara, Firozkohi, Jamshedi and Taimani - live. Their number is estimated at anything from 250 000 to 2 million people. They are Farsi speaking.
In the mountainous regions in the east, mainly in Nuristan Province, live the Nuristani who speak four Indo-Iranian languages. The Nuristani group were the last people in Afghanistan to become Islamised. Up until 1895 when the area was conquered by the Afghan Emir Abdur Rahman, they were called Kafirs (infidels), but were forcibly Islamised after the conquest. A small group of Kafirs who fled to what was then British India, still practise the old religion in Kalash in Northern Pakistan.
On the outskirts of Nuristan live the Pashai, speaking Pashai which is a Dardic language.
Population growth is rapid, 2.6% per year, and 45% of the population are estimated to be under 15 years of age.
Many of the ethnic groups living in Afghanistan are also found in the neighbouring countries of Iran, Pakistan, Turkmenistan, Uzbekistan and Tajikistan. In many cases, there are more of them in neighbouring countries than in Afghanistan.