The rug you choose to place in front of your sofa should be at least as long as the length of the sofa. This creates a sitting area that is the focal point of the room, and it feels very symmetrical. Place the rug slightly under the couch so the nearest corners are covered. This prevents your family members and guests from tripping on exposed rug corners as they sit down on the couch.
Measure the length and width of the open area in front of your sofa if it is a sectional sofa, or if you have placed chairs at 90-degree angles to the ends of the sofa to form a U-shape. Ideally, the rug should cover this open area with its nearest edge slightly under the sofa without any exposed corners to trip over. The rug highlights the enclosed, or partially enclosed, cozy sitting area.
Consider using rugs of different sizes if you need two or more rugs in the room where your sofa sits. Two rugs of the same exact size will cut your room in half, making it feel much smaller that it really is. Lay down a rug in front of the sofa that is at least the length of the sofa. Experiment with smaller rugs near a fireplace or French doors to highlight those areas.
The front legs of the sofa can rest on the nearest edge of the rug, while the back legs will rest on the floor. All of the legs of a coffee table, however, should rest on the rug in front of the sofa. The coffee table should be placed in the middle of the rug and lined up with the middle of the longest section of couch. The rug should be big enough for equal amounts of it to show on all sides of the coffee table.