The world religions statistics used on the homepage of this site are derived from the World Factbook, a publication of the US government.  They give an estimate for total global population, and further down on the page, they estimate the percentage of the global population that believes in or adheres to a set of beliefs about who god is or isn’t.

We simply multiplied the percentage they gave by the total population to come up with the total estimate for each belief.  We recognize these numbers are not as accurate as we would like them to be, but it seems to be the best available information.

Below is the complete list provided by the World Factbook:

Christians  – 2,308,475,658

Muslims – 1,455,614,453

Hindus – 918,679,088

Buddhists – 404,606,778

Sikhs – 24,248,694

Jews – 15,934,856

Baha’is – 8,313,838

Other Religions – 816,141,754

Non-Religious – 815,448,934

Atheists – 160,734,199

Another source for world religion statistics comes from Adherents.com.

Wikipedia.org has several resources on this topic, including a list of religious populations and this image below with further breakdowns of the prevailing denominations throughout the world.