This is a silly photo in which I measure the diameter of my shaft when having an erection. The 41.39 mm (1.6295 inches) would translate into a circumference of ~13 cm or ~5.2" (multiplying the value with pi).

The head is a little thicker. Measured at the “rim” of the head just above the shaft, the scale was at 48.84 mm (1.9228"). Which leads me to think that the circumference is at 15.34cm or ~6" there.

There is a poorly taken picture (it is hard to see where I actually place the instrument) of that as well. Please click or tap here to get a larger view more easily.