Drop an equirectangular 360 photo (2:1, from a 360 camera or a phone 360 app), or choose a file

How it works: with the camera height known, the line where each wall meets the floor gives the distance to that wall. Corners are found automatically for rectangular rooms; drag them onto the real corners if they are off (furniture and open doors can mislead the search). Tested on synthetic 360 photos: room sizes within about 7 cm; real photos depend on the camera height you enter and on lens stitching.