According to Apartment Therapy, the ideal distance between the sofa and coffee table measures about 18 inches. This distance allows for people to move freely between the coffee table and the couch. This should also allow you to place a drink on the table without having to reach too much. You also want to make sure that the table is the proper size in relation to couch. For example, if you place a coffee table that's too large in front of a small couch, you may still have spacing problems. While you may have found the right placement for the coffee table in front of the couch, you may have blocked another walk way on the opposite side of the table, causing an obstruction. It's best to try and determine the distance between all the objects in the room when you're striving for room balance.
The principles of interior decorating suggest that a homeowner follow the triangle guideline when placing furniture in a room. This rationale of this suggests that the most important pieces in a room be placed in a triangle. In the living room, the triangle normally consists of the door or fireplace, the TV and the couch; these items typically stand at the three corners of the imaginary triangle. When placing the sofa in this arrangement, ensure that it's not too close or too far away from the coffee table. It'll pull off the visual balance of the triangle. If you're not sure that you've placed these items in proper alignment, use a floor grid and draw out each piece. This will ensure the proper distance between the couch and the coffee table as well as the other pieces in the room.
If you've made your couch the focal point of the room, make sure that the distance between the couch and coffee table draws attention to the focal point instead of detracting from it. A table that stands too close will detract from the couch, because the couch will have to compete with it for attention. Finally, the height of the coffee table in relation to the couch should only differ by about 4 inches with the table being shorter than the couch.
The rug that you place under a coffee table should serve the overall scheme of the furniture placement as well. Generally speaking, the furniture you place around the rug should at least allow for the front legs of the furniture pieces to rest on the rug. In terms of the coffee table-couch combination, make sure that the front two legs of the couch rest a couple of inches inside the edge of the rug. The coffee table should sit well inside the borders of the rug's edge.