India's population has grown by 181 million people over the past decade to 1.21bn, according to the 2011 census. See BBC report
More people now live in India than in the United States, Indonesia, Brazil, Pakistan and Bangladesh combined. India is on course to overtake China as the world's most populous nation by 2030, but its growth rate is falling, figures show. China has 1.3bn people.
The census also reveals a continuing preference for boys - India's sex ratio is at its worst since independence. Statistics for the past 10 years show fewer girls than boys are being born or surviving. They show 914 girls were born for every 1,000 boys under the age of six, compared with 927 for every 1,000 boys in 2001 census.
"This is a matter of grave concern," Census Commissioner C Chandramauli told a press conference in the capital, Delhi.
Female foeticide remains common in India, although sex-selective abortion based on ultrasound scans is illegal. Sons are still seen by many as wage-earners for the future.
The population of India now comprises 623.7 million males and 586.5 million females.