Bulgaria is 43% larger than Serbia.
Area: 110,879 km2 World Factbook
Population: 6,924,716 (July 2014) World Factbook
Bulgaria, officially the Republic of Bulgaria, is a country in southeastern Europe. It is bordered by Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, and the Black Sea to the east. Wikipedia
Area: 77,474 km2 World Factbook
Population: 7,209,764 (July 2014) World Factbook
Serbia, officially the Republic of Serbia, is a country located at the crossroads of Central and Southeast Europe, covering the southern part of the Pannonian Plain and the central Balkans. Wikipedia