Numbers in millions
Christianity 2,000–2,200 Abrahamic religions Predominant in the Western
world (Europe, the Americas, Oceania), Sub-Saharan Africa, the Philippines, and
East Timor in Southeast Asia. Minorities worldwide, see Christianity by country.
Islam 1,300–1,650 Abrahamic religions Middle East, Northern Africa, Central
Asia, South Asia, Western Africa, Malay Archipelago with large population
centers existing in Eastern Africa, Balkan Peninsula, Russia and China.
No religion 1,100 Secularism Predominant in the Western world. Minorities
worldwide, see Irreligion by country.
Hinduism 828–1,000 Indian religions South Asia, Bali, Mauritius, Fiji,
Guyana, Trinidad and Tobago, Suriname, and among the overseas Indian
communities.
Buddhism 400–500 Indian religions South Asia, East Asia, Southeast Asia,
Australia and some regions of Russia.
Folk religions 400-500 Folk religions Africa, Asia, Americas
Chinese folk religions (including Taoism and Confucianism) 400-500 Chinese
Religions East Asia, Vietnam, Singapore and Malaysia.
Shinto 27–65 Japanese Religions Japan
Sikhism 24–28 Indian religions Indian subcontinent, Australasia, Northern
America, Southeast Asia, the United Kingdom and Western Europe.
Judaism 14–18 Abrahamic religions Israel and the worldwide Jewish diaspora.
Jainism 8–12 Indian religions India, and East Africa.
Bahá'í Faith 7.6–7.9 Abrahamic religions Noted for being dispersed worldwide
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
Cao Dai 1–3 Vietnamese Religions Vietnam.
Cheondoism 3 Korean Religions North and South Korea
Tenrikyo 2 Japanese Religions Japan, Brazil.
Wicca 1 New Religious Movements United States, Australia, Europe, Canada.
Church of World Messianity 1 Japanese Religions Japan, Brazil
Seicho-no-Ie 0.8 Japanese Religions Japan, Brazil.
Rastafari movement 0.7 New religious movements, Abrahamic religions Jamaica,
Caribbean, Africa.
Unitarian Universalism 0.63 New religious movements United States, Canada,
Europe.
Considering the JWs leaders' following as separate from Christianity
otherwise, which the JWs leaders do, it's about 13th on the list after
the Bahá'í Faith.
http://en.wikipedia.org/wiki/Major_religious_groups#Largest_religions_or_belief_systems_by_number_of_adherents
