In Belgium, almost 7% of the Belgian population is Muslim. A scientific figure calculated, on 1 January 2015, by the sociologist Jan Hertogen, who works in particular with the Catholic University of Louvain. According to his calculations, there are 4.9% of Muslims Wallonia and 23.6% in Brussels. Finally, the majority of Muslims in Belgium live in Flanders…Source
An interactive map is available here (link).