Bluetooth devices can be in 3 different power classes:
Class 3 : The lowest power, the max. range of this is 10m (30 feet)
Class 2 : Max range is about 50m (150ft)
Class 1 : Max range is about 100m (300ft)
These ranges can be affected by environmental conditions i.e. furniture, walls, people so ranges can easily be reduced. Bluetooth is not a line of sight connection so it can be used through walls and floors.