The sofa is two thirds of the wall length

All the difficulty of a living room comes down to one simple question: what size sofa? Too small, it floats against the wall and the room looks under-furnished. Too large, it crushes.

The professional rule is mechanical. The sofa must be approximately two thirds of the length of the wall it is placed against. This proportion comes from the same logic as the golden ratio: the eye perceives a slightly unequal ratio as correct, neither half (too symmetrical) nor the full length (too saturated).

Wall is 3 metres, sofa is 2 metres. Wall is 4.5 metres, sofa is 3 metres. No calculation, no interpretation, just a ratio to respect.

Measure the wall from corner to corner without including doors or windows if they break the line. Multiply by 0.66: that is your target sofa length. Tolerance of ± 20 cm.

For a corner sofa, measure the main segment only. If the sofa is freestanding, measure the zone of use (the floor space occupied by the rug or composition).

Visualisation tip before buying. Mark the sofa length on the floor with masking tape. Live with it for 24 hours.

Pierre Yovanovitch sometimes works at 50% when he wants an architectural empty wall effect behind the sofa, compensating with a monumental artwork. The 2/3 rule remains the default.

In lofts and large open-plan rooms, some designers push to 75-80% using very wide modular sofas, only if the room is sufficiently open elsewhere.

Another practice: two sofas facing each other instead of one large sofa. Each sofa is approximately 50% of its wall, the zone of use is delimited by their symmetrical position.