Belgium the Netherlands Population 11,099,554 17,011,595 Area 31 000 km2 (11,969 sq mi) 42 000 km2 (16,216 sq mi) Population Density 364/km2 (942/sq mi) 405/km2 (1,049/sq mi) Capital Brussels Amsterdam Largest City Antwerp – 510,610 (Brussels – 1,830,000 Metro) Amsterdam – 810,084 (1,575,263 Metro) Government Federal parliamentary constitutional monarchy Unitary parliamentary constitutional monarchy Head of State Philippe Willem-Alexander Head of Government Alexander De Croo (Open VLD) Mark Rutte (VVD) Official language Dutch, French, German (de facto and de jure) Dutch, West Frisian (de facto and de jure) Main religions 58% Catholicism, 7% other Christian, 5% Islam, 2% Other, 27% irreligious 29% Catholicism, 19% Protestantism, 5% Islam, 5% Other, 42% irreligious Ethnic groups 59% Flemish, 32% Walloon, 10% other 81% Dutch, 19% other GDP (PPP) $420.307 billion, $37,883 per capita $696.308 billion, $41,447 per capita GDP (nominal) $484.692 billion, $43,686 per capita $800.535 billion, $47,651 per capita