First up, it’s not a magic bullet; despite what Dan Brown may say it’s not encoded with divine hermetic powers but it does turn up a lot in art and nature whether it’s the Parthenon or The Last Supper. In fact there’s an entire Wikipedia page dedicated to works supposedly based on the Golden Ratio.
So what is it? If we were to take two lines – one long (a) and one short (b) with a ratio of 0.618:0.382 this will equal 1.618. Try it on a calculator. Nothing great here.
If we were to to add the long and short lines together then the total of the ratio (a+b:a) would also be 1.618:
Spooky, eh? Not really. This is the Golden Ratio (or Phi).
Similarly a Golden Rectangle has the following proportions which were used for many Renaissance painting frames:
We could create this in Illustrator by just drawing a square and then drawing a diagonal line from the bottom midpoint to the top right-hand corner:
Then rotate the line so it’s running flat along the bottom..:
…and now we have a homemade Golden Rectangle:
So what’s it good for? Well, we can consider it a strategy for layout. Is it the most pleasing proportion? Possibly. But it has been used so extensively it’s worth thinking about when creating a two column grid as was used by Doug Bowman for a since redesigned Twitter layout (illustrated using the Golden Spiral):