Calculation. Summary: This is the calculation used for figuring the yield to maturity of bonds and coupons purchased after 1984. This calculation can only be used if the period from purchase to maturity has a short initial accrual period. To calculate: n multiplied by ((s.r.p. divided by a.p.) raised to the (1 divided by ((r divided by s) plus m) power minus 1): where: n is the number of accrual periods in one year, s.r.p. is the stated redemption price at maturity; a.p. is the acquisition price; r is number of days from purchase to the end of short accrual period; s is number of days in accrual period ending on last day of short accrual period; and m is number of full accrual periods from purchase to maturity.