To calculate the quantity of steel spirals ( or spiral ties) in steel cage (or sometimes rebar cage) for piles ( reinforced concrete or bored pile), you have to have the following informations ( check the details in the drawings) :
a) diameter of pile
b) length of pile
c) pitch of spirals (spacing of spirals)
d) size of spiral (diameter of bar)
Here is a very informative video by SL Khan about Steel Calculation for Pier, Pile and Circular Column Having Spiral.
In this video step by step procedure given with a well introduction about Steel Calculation jobs.
Watch the video.