A comprehensive demographic study of more than 200 countries by the Pew Forum on Religion & Public Life finds that roughly a quarter (23%) of the estimated 2009 world population is Muslim. Overall, there are 1.57 billion Muslims in the world today. The Middle East-North Africa region of the globe contains the highest percentage of Muslims in the world. In more than half of the 20 countries in the region, populations are 95% Muslim or greater. However, just about 20% of the total Muslim population lives in this region. In fact, more than 60% of the global Muslim population resides in Asia. In many of these countries the Muslim population is a minority, but still quite large. India, for example, has the third-largest population of Muslims worldwide. China has more Muslims than Syria, and Russia is home to more Muslims than Jordan and Libya combined.
Source: Pew Research Center