You may be able to calculate the Brake Horse Power (BHP) that you need at the pump, and from that the Running Load Amps (RLA). However motors only come in specific sizes. So after determining the BHP, you select the next size motor that is equal to or greater than the requirement, and then that motor has a FLA rating. From the standpoint of electrical circuit design that is the number you must work with.
"Venditori de oleum-vipera non vigere excordis populi"