An electromagnetic launcher (EML) is used to generate high launching velocities. The basic governing equation of the propulsion force of an EML is that the propulsion force is directly proportional to current and inductance gradient. L ′ is the inductance gradient that refers to the increase or decrease in the inductance with the length of rails. The inductance gradient is easily calculated because it is a function of the rail shape and frequency. However, current ( I ) flowing in an EML is calculated by the series resistor, inductor, and capacitor (RLC) equation of the equivalent circuit. Here, L is not constant and increases as the projectile muzzles. Owing to the increase in inductance, the current ( I ) and voltage ( V ) vary depending on the projectile position. Therefore, inductance, current, and voltage should be exactly obtained to calculate the exact current at a specific time. This study deals with analytical performance prediction using the relation EML propulsion force with real-time current, which is based on an increase in resistance and inductance at a specific time. To validate this approach, the results of the current waves are compared via numerical analyses and experiments. Using this prediction method, it is possible to determine and optimize the rail shape and length from the capacitor bank and vice versa.