9' x 12' rugs are ideal for a larger living areas or bedrooms with a king bed. Transitional and contemporary rugs tend to look better in a 9' x 12' size (or larger) since the design has more space to develop.
On Your Floor:
Ideal for many dining rooms because you can usually keep all four chair legs on the rug.
It is also a large enough size for most living areas to keep all four legs of sofa and armchairs on the rug. It works great if the living area and/or sofa is floating in the room.