Have a go at this without a calculator....

[magicmerlin]

Imagine that you can fold a piece of paper as many times as you want to (we all know it's about 8 times in reality).

This piece of paper is one thousandth of an inch thick (0.001")

You are to fold this piece of paper exactly in half for 50 times.

What is the total thickness from top to bottom of this piece of folded paper?

[magicmerlin]

Would the Rev Green please look at the answer I posted at 20:03 and you will see how well you have done.

[Rollo]

Now with a calculator

(2^50)/1000/36/1760 = 17,769884.893349494949494949 miles.

[magicmerlin]

Rev. Green, I liked your idea of working in metric to get as far as you can then to add on for any minor discrepancies.

Thanks to all the others who gave meaningful answers.

[factor-fiction]

This would be correct if the fold was perfect but I thought that when paper is folded the fold took the form of a semi circle at the ends and the layers do not sit perfectly on top of each other.
Certainly mathematicians refer to the 'loss function' (http://www.its.caltech.edu/~ari/paper-folding. html)
which impacts on the minimum size of the original sheet needed to achieve a given number of folds. So my question for you, magicmerlin, is how big would the original sheet have to be in order to achieve 50 folds?

[magicmerlin]

factor30. It would appear that you have spotted my omission. I should have stated that the piece of paper can be as big as it needs to be. Although it did not stop others having a go. You are now going to ask who can fold a piece of paper that is nearly 9 million miles thick to get to the final thickness, my answer to that is 'don't'. The purpose of the exercise was mental arithmetic.

[dxhound2003]

This was on the Real Hustle on BBC Three recently. The answer for 60 folds is at the end of the clip.

https://www.youtube.com/watch?v=5xm8d8xmqTk