Sizing decides which rug. Placement decides whether it looks deliberate.
Centre it on the furniture
The seating group is what the rug exists to unify, so the rug's centre should be the group's centre — not the room's.
In practice these often coincide. Where they do not, follow the furniture. A rug centred on the room but visibly off-centre to the sofa reads as wrong to almost everyone, even people who cannot say why.
Establish one axis
A rug can only serve one direction
Decide what the room is oriented to — the fireplace, the window, the television, the conversation — and align the rug to that. A rug that tries to acknowledge two competing axes ends up aligned to neither.
Where the fireplace is the focal point and the furniture faces it, the rug should run square to the fireplace even if that is not square to the room.
Traffic routes
Look at how people actually cross the room, and where the rug's edge falls relative to those routes.
An edge in the middle of a walking route gets caught and curls, and eventually the rug gets nudged out of position permanently. Better for a route to cross the rug fully or miss it entirely than to run along its edge.
This is the argument for a larger rug that people walk across rather than around.
Distance from walls
45–60cm of exposed floor, reasonably even. Two practical consequences:
Do not tuck a rug under a wall unit or bookcase. The rug should stop clear of built-in furniture, not disappear beneath it.
Skirting and radiators intrude. Measure to the narrowest point, not the widest — see how to measure your room.
Rooms that fight a rectangle
L-shaped rooms. Treat the two arms as separate zones with separate rugs, or size to the main rectangle and leave the return as floor. Do not stretch one rectangle across both.
Bay windows. Stop the rug short of the bay, or put a small round rug in it as a separate element. A rectangle projecting into a curved bay never resolves.
Chimney breast alcoves. Size to the main rectangle. The alcoves are floor.
Very long rooms. Two zones, two rugs — rug layout rules.
Once it is down
Use a pad, cut 25mm smaller on every side, so the edges lie flat and the rug stops creeping. A rug that moves is a rug wearing itself against the floor — rug pads.
Rotate 180 degrees twice a year. Living rooms usually have the largest windows in the house, and uneven sun fading is permanent — rug colors.
Check the corners. Corners that lift are a trip hazard and the first place a rug gets damaged. If a corner will not lie down, weight it for a week or have the rug blocked — rug repair.
Sizing is covered in sizing living room rugs; what survives the room in living room rugs.
Common questions
Should the rug be centred on the room or on the furniture?
On the furniture, almost always. The seating group is what the rug exists to unify, and a rug centred on the room but off-centre to the furniture looks wrong in a way people notice without being able to name.
Should the rug align with the fireplace?
If the fireplace is the room's focal point and the furniture faces it, yes — align the rug to that axis. If the seating group faces elsewhere, align to the seating. A rug cannot serve two axes.