Drop your panorama here
equirectangular JPG or PNG, 2:1
Frame the shot, then Capture
Floor to the centre of the lens, tape-measured. Every distance scales off this one number — 1 cm out is 1 cm in every metre. There is no default, because a wrong default looks exactly like an answer.
Half a degree of tilt puts a 4.3% spread between one side of the room and the other. Run File › Level: verticals once per panorama.
Without wall planes every ray falls through to the floor, so the disc reports “floor” while you point at a wall. This is what made a 1.47 m TV read 9.43 m.
Order matters. Level → trace room → add surfaces → measure. Each step inherits the errors of the one before it.
A real circle drawn flat on the plane the tool is using. Blue floor, purple wall, green object surface, red too near the horizon. If it floats past what you are pointing at, that thing is off the plane and the number will be wrong.