3 x 5

Foyer

3'x5' rugs are most commonly used in foyers. You will find that most machine made rugs advertised as 3'x5' are actually closer to 3.5'x5.5' and that there are also 4'x6' rugs whose slightly larger size may work out better for some spaces though the selection may be limited.  

Bedrooms

3'x5' rugs can fit nicely on both sides of a bed.