Wire length calculations

[Joey Reich]

forgive me if this has already been covered, i did a search and couldnt find anything......
does anyone have an easy formula for figuring out how the length of wire in an element when it is coiled and unstretched? I was thinking it is something like:

wire lenght per inch of coil = (coil diameter * pi) / wire diameter (in inches)

I dont know how to take into accound the diameter of the wire for the circumference calculation... do i use outer coil diameter or inner coil diameter or outer coil diameter minus wire diameter (to get the coil diameter from the center of the wire: 1/2 wire diameter on top plus 1/2 wire diameter on bottom)

Also, i understand that the coil will need to be stretched to at least double its origional lenght, but i will factor that into my calculations afterwards.

--J

[Steve Stadelman]

I use the mean diameter (coil I.D. plus 1 wire diameter) try to stretch to three times unstretched length.

[Joey Reich]

thanks steve. so the rest of the formula is correct? holy crap! hows that for drudging up random math skills!