it's 78' from the outside edge of one arm to the outside edge of another arm. When everything is slid out and flopped down, the total sleeping space is actually 64" (65 if you count floppy seams) from the top of the back to the feet, leaving a 6 foot person with feet hanging well off, and 68 " including seams from inside arm to inside arm. To take one of the arms off to get them out of the way you have to lift the entire couch. Firm doesn't describe it. It's hard. I bought three different toppers to try on top, none of them fit. Even a little. At all.  It's hard for me to pull out the extenders, and impossible for me to put back the supporting legs. I have to have my husband do it. I needed something I and my mother could use. this isn't it. Now I have spent my money. I tried researching carefully but nonetheless.  The back has three positions to recline, but you can't actually use the middle position since the back is only 17 inches.