What size sofa for your living room? Wall, walkway and proportions

The simplest starting point is the two-thirds rule: the sofa takes up roughly two thirds of the wall behind it. Designers use this proportion because it leaves room at each end for a side table, a lamp or a plant, and it stops the sofa looking squeezed in. A sofa that runs wall to wall also makes cleaning harder, since dust and fine sand gather in the narrow gaps at each end.

Treat the rule as a range, not a law. Anything from a little under two thirds to about three quarters of the wall usually looks right. Much smaller, and a sofa can look lost on a long villa wall; much bigger, and the room starts to feel crowded. Whatever the proportion, keep at least 15 to 20 cm free at each end.

If you know the size of your living room rather than the exact wall, this table gives a first answer. It applies the two-thirds rule to the wall the sofa stands against, and names the shape that usually suits each room. Corner sofas use two walls, so they can run up to about three quarters of the longer one.

The table is a starting point: doors, windows and walkways decide the final size, so measure as shown below. To count the seats your family needs, see how many seats you need; to weigh one shape against another, see 2-seater, 3-seater or corner sofa. And before you order, check that your sofa will fit through the lift and the door.

Three measurements tell you almost everything. Take them with a metal tape measure and write them on a quick sketch of the room.

1. The wall. Measure the length the sofa can really use: from the corner to the edge of anything that interrupts it, such as a column, a window frame, a floor socket you need to reach or an air conditioning unit low on the wall.
2. The depth. Measure from that wall to the opposite wall, or to the front of the TV unit. This decides how deep the sofa and the coffee table can be.
3. The paths. Note where people walk: from the entrance of the room to the kitchen, the balcony or the bedrooms. A sofa should never sit across a route everyone uses.

Also check the height of any window sill behind the sofa. A sofa back that rises above the sill cuts into the window; a low back sits neatly below it and keeps the light.

Walkways are what make a room feel easy to live in. A common rule is to keep about 60 cm free wherever people pass now and then, and 75 to 90 cm on a main route, such as the way from the entrance to the kitchen. In family homes where children run through and guests arrive with trays of food or coffee, the wider figure is worth protecting.

In front of the sofa, the coffee table sits 40 to 50 cm from the edge of the seat: close enough to put down a cup without stretching, far enough for knees and feet. Our coffee table guide has the sizes and heights that go with it.

If the sofa stands against a wall, leave a gap of 5 to 10 cm behind it, so curtains hang freely and the back cushions do not rub the paint. If it floats in the room and people walk behind it, that gap becomes a walkway of 75 to 90 cm.

Width gets all the attention, but depth is where many living rooms run out of space. Add up everything that lines up between the sofa wall and the opposite wall, and compare the total with your measurement. Here is a typical example with a 3-seater facing a TV.

If your room is shorter than the total, there are three easy fixes: a smaller or round coffee table, a wall-mounted TV instead of a unit, or a sofa with less overall depth.

For a corner sofa, check the second direction too. The chaise reaches into the room, so in that direction you need the chaise depth plus a walkway. For the Nuage corner, that is 152 cm plus 60 cm, or 212 cm, if people walk past the end of the chaise.

Two sofas of the same width can feel very different in a room. Three details change their visual weight.

• Back height. A low back keeps sightlines open and makes a room feel larger. The Nuage stands 70 cm high, low enough to sit under most window sills. A taller back, like the Doudou at 85 cm, frames a large villa room and gives more support to your head.
• Depth. Deep seats are made for lounging and curling up, but they use floor space. Compare the overall depth with your depth budget, not only the seat.
• Arms. Wide arms look generous but take seat width. On the Nuage 3-seater, each arm is 28 cm, which leaves about 174 cm of seat between them.

In a big room, scale up rather than spread out: one generous corner sofa usually looks calmer than a small sofa surrounded by chairs. In a small room, choose fewer, larger pieces with clean lines and keep the floor around them clear. Our guide to 2-seater, 3-seater or corner sofas goes further.

Here is how our five sofas line up against the two-thirds rule. The first wall length is where each sofa looks its best; the second is the shortest wall where it still fits with 30 cm to spare.

The Comfo is fully modular, so it appears three times: it comes as a 2-seater, a 3-seater, a chaise, a corner or a U-shape of 5 or 6 modules, and you can separate, join and rearrange the modules whenever your room changes.

To check your own wall, use the Will it fit? tool on each sofa page, for example on the Nuage: type the length of your wall and you see the wall and the sofa drawn to scale, with the centimetres you have to spare. If none of the standard sizes suits your room, you can ask for a custom sofa: the team replies within 48 hours with a drawing and a price.

Numbers on paper are one thing; standing next to the outline is another. Mark the sofa's full footprint on the floor with masking tape: width, depth and, for a corner sofa, the chaise. Add the coffee table if you have one in mind, then live with the outline for a day or two.

Walk your usual routes. Carry a tray past it. Sit on a dining chair placed at the tape line to see where your eyes land in relation to the TV or the view. If anything feels tight with tape, it will feel tighter once the sofa is there.

For a corner sofa, the tape also settles which side the chaise goes. Left and right are always named as seen when you face the sofa, not when you sit on it, and our guide to choosing a left or right chaise explains the simple rule that decides it.