Calculation. Summary: This is the calculation used for figuring the yield to maturity of bonds and coupons purchased after 7/1/82 and before 1985. This calculation can only be used if the period from purchase to maturity can be divided exactly into full accrual periods. To calculate: (s.r.p. divided by a.p.) raised to the (1 divided by m) power minus 1: where: s.r.p. is the stated redemption price at maturity; a.p. is the acquisition price; m is number of full accrual periods from purchase to maturity.