What width is best for parallel bars

Hello, I am in the process of making my own parallel bars for the upcoming dip progressions.

How do I determine what width is best for parallel bars?, most seem to be around 50 cm wide.

Is there a standard width?

Thanks 

Johan

hi Johan the distance it is calculated from person to person as follow below.

Nice, Thanks Alessandro

4 hours ago, Alessandro Mainente said:

hi Johan the distance it is calculated from person to person as follow below.

Just to be completely sure, does this mean whole forearm plus open hand width? This seems to be a little bit wider than shoulder width.