How do I know if a sofa is too big for my room?
Three checks catch almost every oversized sofa. Measure the wall it will stand against, keep 75–90 cm of walkway in front of it, and confirm it fits through the door it has to come in by.
Wall first. A sofa should leave a hand-width of wall at each end, otherwise the room reads as full even when the sofa technically fits. If your wall is 260 cm, a 240 cm sofa is already tight.
Walkway second, and this is the one people skip. The space between the sofa and whatever faces it needs to stay walkable. Under about 75 cm you start turning sideways to pass, and you will notice it every day.
The doorway third. This is the check a picture cannot do for you: the sofa has to physically arrive. Compare the sofa depth and height against your narrowest doorway and any turn in the hallway or stairwell.
A preview in your own room settles the first two quickly, because it puts the sofa next to your real window and your real door instead of a showroom. The third one needs a tape measure and always will.