Matthew Poole and continuators on Ezekiel 40:15

15 And from the face of the gate of the entrance unto the face of the porch of the inner gate were fifty cubits.

This verse seems to summe up all the dimensions at length this gate, its porch, and thickness of its walls, and so summe the cubits, 6 in the thickness of the outer wall, 18 in the three chambers, 20 in the spaces between the chambers, and 6 cubits in the thickness of the inner wall of the porch.