I recently came across this fact:

There's enough DNA in the human body to stretch from the sun to Pluto and back.

A couple of "Bollocks!" alarms began to chime in my head. While I expect that it will stretch a long way, Pluto seemed a little far-fetched. Looking this up further led me to this page which actually calculates the figure in some detail. The final result came to around 2x1013 metres or ~134AU.

In the interest of keeping things manageable, I'm going to use AU from here on in.

Discover Magazine might be the source of the Pluto analogy:

Don’t try this at home: If uncoiled, the DNA in all the cells in your body would stretch 10 billion miles—from here to Pluto and back.

10B miles = 10B * 1.62 / 150M = 108AU

The mean distance between Pluto and the Sun = 39AU. Distance between the Earth and Pluto and back = (39 - 1) * 2 = 76AU

Another page claims:

If you could unwrap the DNA you have in all the cells in your body, you would be able to reach the moon and back 6,000 times. This would be a distance of:

384000 * 2 * 6000 = 4608M Km ~= 31AU

Unless my calculations are ridiculously flawed, something is amiss here. While I'm flabbergasted that just the DNA in a human body can stretch to, well, almost three times the distance of Pluto from the Sun, it appears that most, if not all these analogies are incorrect. So, my question is: If all the DNA in an adult human body were to be uncoiled and stretched out, how long would it actually stretch for?