Kierkegaard, D. Anthony Storm's Commentary on. History of Religion. Major Religions Ranked by Size. Christianity > Anglican | Catholic | Evangelical | Jehovah's Witnesses | Latter-day Saints | Orthodox | PentecostalIslam | Hinduism | Buddhism | Sikhism | Judaism | Baha'i | Zoroastrianism | more links (Sizes shown are approximate estimates, and are here mainly for the purpose of ordering the groups, not providing a definitive number.
This list is sociological/statistical in perspective.) A major source for these estimates is the detailed country-by-country analysis done by David B. Barrett's religious statistics organization, whose data are published in the Encyclopedia Britannica (including annual updates and yearbooks) and also in the World Christian Encyclopedia (the latest edition of which - published in 2001 - has been consulted). Hundreds of additional sources providing more thorough and detailed research about individual religious groups have also been consulted.
Christian. Muslim.