Electron volt is defined as the amount of energy one electron gains by moving through a potential difference of one volt. Hence, one electron volt is equal to elementary charge (1.60217657 × 10-19 coulombs (C)) multiplied by one volt. It can be written as
ev = (1.60217657 × 10-19 C) (1V)
Therefore, 1ev = 1.60217657 × 10-19 J.