Alrighty , so Wikipedia says the Muslim population is around 1 . 6 Billion in 2010 , and with the worlds population being 7 . 4 , this is essentially 1 . 6 Billion people Vs 5 . 8 Billion people . is a graph showing Muslim population throughout the world . If all Muslims suddenly get a bloodlusted urge to kill everyone ' s outside their religion , they ' ll be centred around Northern Africa and the Middle East , with some of those AsianOceanic Islands as well . The Northern African countries would probably take the Southern countries , but that wouldn ' t really make a difference . Once the world finds out what ' s going on which won ' t take long after small Muslim communities all over the world start murdering people , America , Europe , Russia and Asia will come down like a ton of bricks , working together to wipe out the threat . As for the different scenarios , I don ' t have a source on this , just speculation , but it seems people are getting less and less religious as the years go on , meaning less people for the Islam side in 50 100 years .