After the 2011 Census, Bihar was the third most populous state of India with total population of 104,099,452 (54,278,157 male and 49,821,295 female). Nearly 89% of Bihar's population lived in rural areas. The density was 1,106. The sex ratio was 918 females per 1000 males. Almost 58% of Bihar's population was below 25 years age, which is the highest in India. Most of Bihar's population belongs to Indo-Aryan-speaking ethnic groups along with few Dravidian-speaking and Austroasiatic-speaking people mostly in Chhotanagpur Plateau (now part of Jharkhand).Bihar has a total literacy rate of 61.80% (71.20% for males and 51.50% for females), recording a growth of 20% in female literacy over the period of a decade.

At 11.29%, Bihar has the second lowest urbanisation rate in India. As per of the 2011 census, Bihar is India's most densely-populated state.

Largest cities in Bihar
	City	District	Population			City	District	Population
1	Patna	Patna	20,46,652		8	Arrah	Bhojpur	2,61,430
2	Gaya	Gaya	4,70,839		9	Begusarai	Begusarai	2,52,008
3	Bhagalpur	Bhagalpur	4,10,210		10	Katihar	Katihar	2,40,565
4	Muzaffarpur	Muzaffarpur	3,93,724		11	Munger	Munger	2,13,303
5	Purnea	Purnea	3,10,817		12	Chhapra	Saran	2,12,955
6	Darbhanga	Darbhanga	3,06,089		13	Saharsa	Saharsa	1,56,540
7	Biharsharif	Nalanda	2,97,268		14	Hajipur	Vaishali	1,47,688
Source: Census of India 2011