Choose the right area rug size for a bed, sofa or dining table.
Rug sizing is governed by clearances rather than by taste, and each placement has its own. Under living room seating the rug should extend about eighteen inches beyond the sofa so the front legs and the coffee table sit on it and the arrangement reads as one zone. Under a bed, two feet each side gives a soft landing where you actually step. Under a dining table the figure is thirty inches, because a chair pulled out must stay entirely on the rug — a back leg dropping off the edge is the single most common rug mistake, and it makes the chair rock every time someone sits down. The room then sets an upper bound: a rug should leave a border of bare floor, so this caps the recommendation at roughly a foot and a half in from each wall before matching to the nearest size actually manufactured.
Rug dimensions from furniture and clearances
Ideal size = furniture dimension + 2 x clearance, where clearance is 18 in for seating, 24 in for a bed and 30 in for a dining table; capped at room dimension minus 36 in, then matched to the nearest stock size
Because a dining chair travels roughly two feet when pulled out to be sat on. Thirty inches keeps all four legs on the rug through that movement — if a back leg drops off the edge the chair rocks and the rug wears at that point.
In a living room the front legs of the seating are enough and often look better, since a fully-on layout needs a much larger rug. Under a bed and a dining table everything should be on it.
Go up rather than down. An undersized rug makes a room look smaller and leaves furniture stranded off its edges, which is the more common and more noticeable error.