This article addresses the analytical determination of an "F" factor, used to calculate the value of installments in forward sales. This factor, which is calculated according to the conditions of sale, provides the value of the periodic installments when multiplied by the price of the good sold. Initially, the general formula of the "F" factor is deduced and, later, some particular cases are presented. Finally, hypothetical examples are simulated to facilitate understandingThis article addresses the analytical determination of an "F" factor, used to calculate the value of installments in forward sales. This factor, which is calculated according to the conditions of sale, provides the value of the periodic installments when multiplied by the price of the good sold. Initially, the general formula of the "F" factor is deduced and, later, some particular cases are presented. Finally, hypothetical examples are simulated to facilitate understanding