How can a square peice of paper be folded into a perfect pentagon?

Question

I know a simple square can be formed into a perfectly equilateral five-sided polygon by just a few simple folds, but I'm having trouble finding a way to make it perfect every time. Most methods I have found involve a little guess work. Is there a way to make it perfect every time?

Answer 1

Check out addendum 2 on the following:

http://www.jimloy.com/geometry/pentagon.htm

Answer 2

I did it but it required a precise ruler and a calculator. I don't think that it can be done "easily" because the angles and fold lengths, at least for me, were not "nice" numbers.