Accoring to Wikipedia:
Foreign fighters in Iraq and Syria
There are an estimated 15,000 fighters from nearly 70 countries in ISIL's ranks. According to an UN report.
Statistics gathered on a nation by nation basis indicate:
7,000 from Saudi Arabia
2,400–5,000 from Tunisia
500–2,000 from the United Kingdom
1,000 from the Russian Federation
1,000 from Turkey
900 from France
550 from Germany
300 from China
250–400 from Belgium
250 from Australia
150 from Sweden
140 from Norway
130 from Canada
130 from the Netherlands
100 from the United States
100 from Denmark
50 from Finland
40–50 from Israel
40 from Spain
