India's population, as on 1 March 2011 stood at 1,210.9 million (623.2 million males and 587.6 million females) in compared to a total of 1, 028, 737, 436 in the year 2001. In absolute term, the population of India has increased by more than 181 million during the decade 2001-2011.
The population at the turn of the twentieth century was around 238.4 million. It has grown steadily at each decennial census from 1901, except for a decrease during 1911-21.
Uttar Pradesh is the most populous state in the country with almost 200 million people. Sikkim is the least populous state with 6,07,688 people.
Source: India Book 2020 - A Reference Annual