Relationship Between Six-Month Forward Rates and Spot RatesIn general, the relationship between a t-period spot rate (zt), the current six-month spot rate (z1), and the six month forward rates iszt = [(1 + z1) (1 + f1) (1 + f2) ··· (1 + ft –1)]1/t – 1 where ft is the six-month forward rate beginning t six-month periods from now.Other Forward RatesIt is not necessary to limit ourselves to six-month forward rates. The spot rates can be used to calculate the forward rate for any time in the future for any investment horizon.