I am a fairly large man at 6'4". My thumb, at the knuckle, is 1" wide (this is is being generous it's more like 7/8ths but lets round it up)



Assuming rootbeer's thumb is the same width (again, being generous, he's much shorter than me) we can use it to measure the size of his "dick"



From base to tip it is just under 4 inches fully erect, which matches what lisa has told us.