HA!!
The few serious estimates I found as a kid were for a six inch* length and three inch circumference (could be off on that one), both give or take 3/4 inch or so.
*this long: |<---->|
The ladies have never said mine tastes bad. That could be the difference between circ/uncirc.
There is a link here (third link down)
http://www.skeptics.com.au/features/links/lucky7.htm
I havent clicked to open it (apparently there are pictures and I am at work), so I dont know if it works.