Belgium is 51% larger than Slovenia.
Area: 30,528 km2 World Factbook
Population: 10,449,361 (July 2014) World Factbook
Belgium, officially the Kingdom of Belgium, is a federal monarchy in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters as well as those of several other major international organisations such as NATO. Wikipedia
Area: 20,273 km2 World Factbook
Population: 1,988,292 (July 2014) World Factbook
Slovenia, officially the Republic of Slovenia, is a nation state in southern Central Europe at the crossroads of main European cultural and trade routes. It borders Italy to the west, Austria to the north, Croatia to the south and southeast, and Hungary to the northeast. Wikipedia