5x8 is the first true dining room or sofa rug. This works best for small dining room tables that can fit all chairs on the rug. It also works best square to your sofa, with two chairs on each side and an optional coffee table on the rug.
Placing the correct size rug in your space is as important as choosing the right color or pattern. A rug that it is too small will shift the balance of the room unfavorably. A rug that is too big, especially in open floor plans, may put the area designations off. There are a few rules of thumb, but a picture says it better. Use these handy guides by Interior Designer Lisa Ferguson to make the best choice.