the official census data of indian govt. is different from cia. pleas take a look below TABLE 21: DISTRIBUTION OF POPULATION BY RELIGION Religion Number % All religious communities 1,028,610,328 100.0 Hindus 827,578,868 80.5 Muslims 138,188,240 13.4 Christians 24,080,016 2.3 Sikhs 19,215,730 1.9 Buddhists 7,955,207 0.8 Jains 4,225,053 0.4 Others 6,639,626 0.6 Religion not stated 727,588 0.1 Source : Religion, Census of India 2001 Census of India: Religion Pew research center usually gives result on the basis country's previous census ,population growth. buddhist,jain,sikh together makes up 3.1% of india's population. apert from them there has many small religious group specially in north east india,and country's other tribal area.