How do you know what size furniture fits in your home when you shop online? That's a good question. Just look at your room measurements. If your wall is 120 inches, you're buying a sofa that's 95 inches, pretty certain that's going to fit in there, and then put the coffee table around it, the end tables, the lamps, pictures, mirrors. You're good to go.
So just basic math. If the room, if you're going to put a king-size mattress in the bedroom, and the bedroom is only 10 feet wide, that king-size mattress being 78 across is going to eat up a lot of that bedroom. So it's up to you, but just look at the room, and if you've got space on both sides, you're probably good to go.