The Pew Research Center Forum on Religion & Public Life said its study was based on demographic data from 232 countries and territories. The study found Muslims inhabit all five continents but more than 60 percent of them are in Asia, and another 20 percent are in the Middle East and North Africa.
The Middle East-North Africa region has the highest percentage of Muslim-majority countries, with more than 20 countries and territories reporting a Muslim population of 95 percent or more.
About one-fifth the world's Muslim population, or more than 300 million, live countries where Islam is not the majority religion.
India, which is predominantly Hindu, has the world's third-largest Muslim population. China has more Muslims than Syria, while Russia is home to more Muslims than Jordan and Libya combined, the study said.
Of the world's total Muslims, 10 percent to 13 percent are Shiites while 87 percent to 90 percent are Sunnis. Between 69 percent and 80 percent of all Shiites live in Iran, Pakistan, India and Iraq, the study fund.