<P> Adherents of Islam constitute the world 's second largest religious group . According to a study in 2015 , Islam has 1.8 billion adherents , making up about 24 % of the world population . Most Muslims are either of two denominations : Sunni ( 80 - 90 % , roughly 1.5 billion people ) or Shia ( 10 -- 20 % , roughly 170 - 340 million people ) . Islam is the dominant religion in the Central Asia , Indonesia , Middle East , South Asia , North Africa , the Sahel and some other parts of Asia . The diverse Asia - Pacific region contains the highest number of Muslims in the world , easily surpassing the Middle East and North Africa . </P>
<P> Adherents of Islam constitute the world 's second largest religious group . According to a study in 2015 , Islam has 1.8 billion adherents , making up about 24 % of the world population . Most Muslims are either of two denominations : Sunni ( 80 - 90 % , roughly 1.5 billion people ) or Shia ( 10 -- 20 % , roughly 170 - 340 million people ) . Islam is the dominant religion in the Central Asia , Indonesia , Middle East , South Asia , North Africa , the Sahel and some other parts of Asia . The diverse Asia - Pacific region contains the highest number of Muslims in the world , easily surpassing the Middle East and North Africa . </P>
where does islam rank in size on the list of the world 's religions
where does islam rank in size on the list of the world 's religions
second largest
second largest