In the showroom, lie down on the sofa as you would at home to stretch out, and see if it is comfortable. Also, if the sofa has very thick and wide arms, you might want to consider a sofa with the same inside width but with narrower arms so as to offer you the same ability to stretch-out but without the largeness of the sofa for the room.

This post was edited by Tibbrix on Fri, Jul 25, 14 at 9:11

In my opinion, it's not about what's average, it's about what is logical for the space.

I think you need to do some space planning. Some people do this with graph paper and drawings, so people do it with a measuring tape and the actual room.

Decide the location in the room where the sofa is going to go, decide whether you will have side tables. Think about having chairs facing the sofa so that the people on the sofa can have a conversation with other people in the room. Then measure the available space for the sofa.

"Average" for a one piece sofa is 7 feet +/- a few inches based mostly upon arm style. This is a decent length for someone to lie down on, and depending upon arm style someone may be able to sit at one end while someone else is lying on it.

Part of the sizing also has to do with getting it in and out of the house through doorways and/or up and down stairs, in elevators and such.

I have an 8 foot sofa that will not negotiate the house to where I would like to put it. We will need to keep it where it is, hoist it up to the third floor on the outside and get it in that way or sell it.

I know someone who had to pay a premium to temporarily override one of the automatic elevators in their highrise so it could be attached to a special hook on the bottom of the elevator and the elevator run manually to the right floor.

Then they had trouble getting it in from the hallway. This was a nine footer.

If you live in a large suburban style house maybe none of this matters but that, as well as back height and seat depth are all factors in sofa sizes.

Thanks for all the responses - I know it's kind of a clueless and all-over-the place question and now I've narrowed it down to the main issue, which is navigation. (A side issue is confusion over how it "felt" in the showroom versus the reality of the measurements - I knew from the measurements that it would FIT in the space, but realizing, "wait a minute, that's over 8 feet long (!)" makes me think twice.) We have moved from your average suburban-style house and have downsized to a third-floor walk-up apartment. The interior space is decent but moving anything is a pain and there are FOUR doors through which anyone must pass to enter the apartment. (The doors are wide enough so there's no problem from that standpoint.) I do think the longer couch would work in the space (I had wanted it to go in front of about 11 feet of bookshelves we're installing) but the loveseat could work too, design- and function-wise.

We currently have a loveseat but its official end-to-end width measurement is close to a foot shorter than the loveseat version of the couch in which I'm interested, with fatter arms. This current loveseat is long enough for two average-sized people to sit comfortably facing forwards, but is shorter than I would like for sprawling out. (Depth is also a problem.) I really wanted something longer than this, but am not sure that I need something almost 3 feet longer. I'm thinking that despite the "loveseat" name, the new option is bigger than a typical loveseat. Since whatever we buy will replace the current loveseat, the current loveseat is giving me some idea of what size will look good in the space.

I guess I'm trying to figure out if 8+ feet is a "normal" sized couch which people move all the time into a variety of housing types, or will end up being a big problem. Yes we can measure the stairwell but it will still be hard to say "yay" or "nay." Certainly people move their furniture in and out of this building all the time and it should accommodate "typical" pieces, but is a 99 inch couch considered oversized?

(Re: seating 3 people - do you personally go by cushion count? The 8+' two-cushion couch is explicitly considered a 3-seater but despite its extra length, I suppose doesn't really seat any more people than the loveseat unless someone is sitting on the gap between cushions. But it seems awfully long to only seat two.)

Oh, also, I have a scale floor-plan of the apartment and had worked out some furniture arrangement but not doing that all the time, the reality of the space vs. how it looked on paper was a little jolting.

This post was edited by lizzie_nh on Fri, Jul 25, 14 at 10:56

I think a 9-foot piece would be considered oversized when thinking about moving it as it would be difficult to get around corners and through doorways. I copied the following from a moving site that talks a bit about how a sofa's measurements relate to moving through a doorway which may be helpful to you as you would know the standard sizes of doors in the houses/apartments where you live.

There are two lengths that are most important: the sofa width and the height of the sofa's back (the back of the sofa when you're sitting down - measure from floor to top of back). Let's start there.

Measure the dimensions of the sofa: height, width and length. If the sofa legs can be removed, it's best to remove them first. If they cannot be removed, then you need to measure the height with the legs attached, from the floor to the top of the sofa's back.

Measure the dimensions of the opening, whether it's a door or stairwell or elevator door.

If the sofa's back height is longer than the door's width, then the sofa's width will need to be narrower than the door's width.For example, a door's width is 40" and the sofa's width is 43" and the sofa back height is 38". This means you can turn the sofa so that the sofa's back is facing the ceiling.

The sofa should slide through as long as the inside space will accommodate it (hallway or foyer).

If both the width and the back height is too long for the width of the door, then you need to consider the sofa's length. Measure the length of the sofa and the height of the door opening. The sofa's length will need to be shorter than the door's height.Also check the entrance way to see how much room you have to maneuver - there should be at least a foot or more of space on either side of the doorway in order to shimmy the sofa through. If the inside space is a narrow hallway, the couch may not fit. You may also need to remove the door in order to gain some additional room.

Stand the sofa on one end with the bottom, where the feet are, positioned to enter the doorway first. Now angle the sofa so the back and the bottom form a V. If you're behind the sofa, about to push it through the door, you should be looking at the sofa back and part of the bottom. The sofa's seat should be facing inside.

With someone on the inside and someone on the outside, angle the sofa by sliding the seat through the door, letting the sofa curl around the doorway.

Yes, don't forget about the depth.
My sister fell in love w/a sofa & loveseat in a dept store--they were both the right length, felt comfortable, etc...she didn't think about depth because she was in love w/the upholstery fabric.
They were each 4ft deep, in an open atmosphere like a showroom you can't always correctly visually judge size.

Now in a big room no issue, but when your LR is only 12ft wide, by the time the sofa/loveseat made an 'L', she had 2 ft of space on one end, plus adding big square coffee table and path space around took up that space too across the room.

Luckily, for only another delivery fee she was able to return the pieces.
Lesson learned for next set.

We have an 84 inch couch. In the living room, it was fine but decided to move it to the family room (I like to lay down to read and watch TV). It is really too long (for me and for the room). I am thinking that I need no longer than a 6'5" couch (77 inch) (inside measurement of the arm to arm). Will be looking for that next spring and make do with what I have till then.,

I'm in the same predicament. The wall where my sofa will go is 11' wide and the room is 12' long. Do I go with a 53" loveseat with plenty of space around it? Or choose the 78" sofa version that probably will look too big for the space but its lines are more elegant than the loveseat because it's longer Thanks.