Strain is additive, so total strain [ε]N, incremental strain [ε]i, and number of steps N are related:
[ε]N = N [·] [ε]i
reduction r is related to initial area A0 and final area A, regardless of number of steps, by:
r = (A0-A)/A
and reduction ratio RR for a single step is
RR = A0/A = exp ([ε]i)
or for multiple steps
RR = A0/A = exp (N [·] [ε]i)