Getting the sofa through the living room or apartment doorway is one of the most troublesome chores of moving out of an old dwelling or into a new one. Unless the doorway is wide, you probably won't be able to carry the sofa through upright; you'll probably have to tilt it. Even tilted, though, the sofa may not fit, and you might have to hoist it onto a balcony or disassemble it to get it in or out. Before you get the sofa stuck or into an awkward position, measure it to see if it fits.
Measure the width of the doorway with a tape measure. If it looks like the sofa will be a tight fit, take the door down and measure between the door stops. You can typically gain an extra 1 1/2 inches by prying off the stops.
Use the tape to measure the width of the sofa from the front of the seat to the far edge of the back. If this distance is less than the width of the doorway, you can carry the sofa through upright.
Find the midpoint of the armrest and measure the diagonal distance from here to the rear bottom corner of the sofa. Don't include the legs in the measurement; you'll probably have to remove them. If this distance is less than the width of the frame, you should be able to tilt the sofa to get it through the door.
Determine whether the sofa will fit through the door standing on its end by measuring its length and comparing that to the height of the doorway. If the sofa is short enough to fit, measure the vertical distance from the top of the armrest to the bottom. If it's less than the width of the door, you can stand the sofa on its end, push the backrest through the door, turn the sofa through 45 degrees and push it the rest of the way.