
Popularity
The world’s largest religion is Christianity, with around 2.1 billion followers. Coming in second are Muslims, with approximately 1.5 billion faithful. Catholics make up around 1.1 billion Christians, while Sunnis comprise nearly 1 billion Muslims.
Symbols
Christianity: Cross
Islam: Crescent
Hinduism: Aum
Buddhism: Dharma Wheel
Judaism: Star of David

Quick Facts
According to a Pew study, Christians make up the vast majority of religiously affiliated in the United States, at 70%. Those who say they are unaffiliated with a specific religion number roughly 22%. Of the unaffiliated, atheists make up 3.1% while agnostics number 4%.
Buddhism is practiced by half a billion people around the world, mostly in Asia. Buddhists are nontheistic in belief, instead of embracing various spiritual philosophies.
Hinduism, the third-largest organized religion (1 billion strong), is also the oldest religion on record.
Judaism is followed by roughly 13.4 million people around the world, with 42% of Jews living in Israel and another 42% living in North America.