Nobody knows. This is a political hot-potato. Some non-Muslims have accused Muslims of exaggerated their numbers in order to obtain more political clout. Some Muslims have accused non-Muslims of releasing false, low numbers in order to "marginalize" Islam. Estimates of the number of Muslims in North America range from a little over one million adults to seven million adults and children. One cause of the disagreement appears to be related to the percentage of Muslim immigrants: 1. Who have abandoned Islam since they arrived in the US, or 2. Who still consider themselves to be Muslims, but who do not participate in mosque activities. Estimates include: Date Number of Muslims Source. 2001- 1.1 million adults; 1.8 million adults and children ARIS study 2000 1.6 million Glenmary Research Center 2001-OCT 1.9 million National Opinion Research Center 2001-APR 2 million Muslims Hartford Institute for Religious Research 2001 2.8 million American Jewish Committee 2001 4.1 million Britaininca Book of the Year. 2001 A little over 5 million Abdul Malik MUjahed 2001 5.78 million World Almanac 1995 6 million CAIR 1997 6.7 million Ilyas Ba-Yunus 2001 -APR 6 to 7 million Prof. Ihsan Bagby 2001 7.0 Four Islamic groups 2002 7.0 CAIR 1998 12 million Pakistani newspaper