How to calculate the % of return of writing options?

[FirstTry]

say i short a call and collect the premium, and later on the call expires wirthless. from the view of the options seller, the premium is the profit.

but how do you calculate the % of return? my guess is premium over initial margin? but different broker will set up different initial margin requirement...

any thoughts?

 

[JoeyDVivre]

You don't calculate % return on derivatives.....

 

[FirstTry]

Thanks, Joey.