“Three-seater” describes a cushion count, not a capacity. Take a 205 cm sofa with 18 cm arms: the usable seat is 169 cm. Split three ways that is 56 cm per person. An adult sitting upright needs 60–65 cm shoulder to shoulder, and two adults plus a teenager need more.
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The arithmetic for common widths
| Overall width | Arms | Usable seat | Per person (3) | Real capacity |
|---|---|---|---|---|
| 180 cm | 2 × 15 cm | 150 cm | 50 cm | 2 adults, tight; 3 children |
| 190 cm | 2 × 16 cm | 158 cm | 53 cm | 2 adults + 1 child |
| 205 cm | 2 × 18 cm | 169 cm | 56 cm | 3 upright, 2 lounging |
| 220 cm | 2 × 18 cm | 184 cm | 61 cm | 3 adults, genuinely |
| 235 cm | 2 × 20 cm | 195 cm | 65 cm | 3 adults with room |
| 250 cm | 2 × 20 cm | 210 cm | 70 cm | 3 adults + 1 child |
The threshold sits at 220 cm overall for a sofa that three adults can sit on without touching shoulders. Below 210 cm, the third seat works for a child or for twenty minutes.
Armrests are the hidden tax
Arms run from 12 cm on a slim Scandinavian frame to 25 cm on a deep American-style sofa. On a 205 cm sofa, going from 15 cm arms to 22 cm arms removes 14 cm of seat — nearly a quarter of a person. If seating capacity matters more than looks, choose arms under 18 cm or a chaise-end design where one end is open.
Corner and L-shaped sofas beat straight sofas on capacity per centimetre of wall. A 251 cm corner sofa with a reversible chaise seats four to five because the corner itself becomes usable space, while a 251 cm straight sofa still gives three.
Width is not the only number that limits seats
- Seat depth over 62 cm pushes shorter users forward onto the edge, so they take up more width than they need and the cushion beside them goes unused.
- Fixed back cushions eat 10–15 cm of usable depth; loose back cushions can be removed to gain a seat when guests arrive.
- Seat height below 38 cm makes standing up harder for older guests, which effectively retires one end of the sofa.
- One long cushion instead of three looks cleaner but removes the visual cue that tells people where to sit, and everyone drifts to the middle.
How to check before ordering
- Find the seat width in the spec, not the overall width. If it is not listed, subtract the arm widths from the total.
- Divide by the number of seats you actually need, at 60 cm each.
- Add the room: the sofa should take no more than two thirds of its wall, with 60 cm of walkway in front.
- Check the doorway. A 220 cm sofa needs 80 cm of clear door width and a diagonal route — see the five measurements guide.
The full width, depth and clearance tables are in the sofa size guide. If the room is the constraint rather than the sofa, start with the small living room layouts.
Keep reading
More dimension guides are in the collection, and the full index is on the furnolio journal.
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