Measure wall to wall and type it in. The short walls are the ones the ceiling comes down to; the peak is over the middle.
Solid. The house is 22 ft along the street by 28 ft deep, off the city assessor's own building sketch. Take off the outside walls and the inside width across the front is about 21 ft. That is the wall the window is in.
Solid. Built 1927, one and a half storeys, 924 sq ft finished. The ground floor is 616, so about 308 is counted upstairs.
A guess. 13 ft 6 in front to back is just half the inside depth. No record says where the wall behind this room actually is. Measure that first.
A guess. The short walls at 4 ft and the peak at 8 ft. The gable faces the street, so the ceiling really does slope down to both long walls, but nobody has measured how far. Those two numbers change what fits more than anything else here.