Which religion is the largest in the world?

According to a major 2025 Pew Research Center study using 2020 data, Christians number about 2.3 billion, or 28.8 percent of the world population. Muslims are second at about 2 billion, or 25.6 percent, and Islam was the fastest-growing major religion between 2010 and 2020, largely because of a young population and high birth rates. People with no religious affiliation form the third-largest group, at about 1.9 billion. Hindus number around 1.2 billion, most of them in India, and Buddhists about 324 million. Christianity is the most geographically widespread faith, with large populations on every inhabited continent.