Original: With an estimated number of adherents that ranges between 1.5 billionAdherents.com Number of Christians in the world and 2.1 billion , split into around 34,000 separate denominations , Christianity is the world 's largest religion .
Simplified: Demographics With an estimated number of Christians being somewhere around 1.5 billion to 2.1 billion , split into around 34,000 different denominations , Christianity is the world 's largest religion .