What length for paracord sling?

[cbrdave]

Hi all, I am looking at making a new sling for my camera but don't know how much I need.
I am looking at the cobra style,
Do I just measure my current sling and then double the measurement?.
I don't mind buying too much as you can never have too much paracord, I just don't want to guess and them end up short.
Thanks for any help and advice.

 

[Mesquite]

 

[cbrdave]

Thanks, I'll have a watch.