From Wikipedia
The population numbers below are computed by a combination of census reports, random surveys (in countries where religion data is not collected in census, for example USA or France), and self-reported attendance numbers, but results can vary widely depending on the way questions are phrased, the definitions of religion used and the bias of the agencies or organizations conducting the survey. Informal or unorganized religions are especially difficult to count. Some organizations may wildly inflate their numbers.
Religious category Number of followers Cultural tradition Main regions covered
Christianity 2,100,000,000 – 2,200,000,000[6][7] Abrahamic religions Predominant in the Western world (Europe, the Americas, Oceania), Sub-Saharan Africa and the Philippines. Minorities worldwide, see Christianity by country.
Islam 1,300,000,000 – 1,600,000,000[8][9] Abrahamic religions Middle East, Northern Africa, Central Asia, South Asia, Western Africa, Indian subcontinent, Malay Archipelago with large population centers existing in Eastern Africa, Balkan Peninsula, Russia, Europe and China.
Hinduism 950,000,000 – 1,400,000,000[10] Indian religions Indian subcontinent, Fiji, Guyana, Trinidad, Mauritius, Suriname, Bali, Australasia, Northern America and Southeast Asia.
Buddhism 250,000,000 – 500,000,000[11] Indian religions Indian subcontinent, Sri Lanka ,East Asia, Indochina, regions of Russia.
Sikhism 20,000,000 - 30,000,000[12] Indian religions Indian subcontinent, Australasia, Northern America, Southeast Asia, the United Kingdom and Western Europe.
Judaism 12,000,000 – 18,000,000[13] Abrahamic religions Israel and Jewish diaspora (meaning mostly North America and Europe)
Bahá'í Faith 7,600,000[14] – 7,900,000[15] Abrahamic religions Noted for being dispersed worldwide[16][17] but the top ten populations (amounting to about 60% of the Bahá'í World Faith adherents) are (in order of size of community) India, United States, Vietnam, Kenya, DR of the Congo, Philippines, Zambia, South Africa, Iran, Bolivia[18]
Jainism 6,000,000 – 12,000,000[19] Indian religions India, and East Africa
Cheondoism 3,000,000[20] Korean North Korea
Tenrikyo 2,000,000[21] Japanese Japan, Brazil
Cao Dai 1,000,000 - 3,000,000[22] Vietnamese Vietnam
African traditional and diasporic religions 1,000,000s[23] Folk religions Africa, Americas
Other folk religions 1,000,000s[23] Folk religions India, Asia
Ahl-e Haqq 1,000,000[24] Iranian Iraq, Iran
Seicho-no-Ie 800,000[21] Japanese Japan
Yazidism 700,000[25] Kurdish mainly Iraq
Rastafari movement 700,000[26] Abrahamic religions c. Jamaica, Caribbean, Africa
Unitarian Universalism 630,000[27] Western United States, Europe
Chinese folk religions Varies[23] Folk religions China
Shinto Varies Far Eastern religions Japan
Taoism Varies[23] Far Eastern religions China and the Chinese diaspora
