Hey guys, I am looking for a formula to calculate my Final drive and roll out.

I am running a Custom Works Electric Sprint with a 1:1 direct drive trans.
how do i figure the final drive and roll out for this?

also i am running a B4 (super stock class) chassis with the 2.6:1 trans
How do i figure the final drive and roll out for this one too.

I have been searching on roll out but nothing seems to take in consideration of a 2.6:1 trans..
need some clarification guys!!
thanks