This paper proposes a simple method for calculating the lightning impact level on overhead transmission power lines, taking into account its entire length. The method uses lightning historical data and the geographic coordinates of power line towers. It is based on calculating the distances between both arrays of lightning and of towers. The method has been tested on overhead lines in the Murmansk region of the Russian Federation and can be applied to any overhead line if a lightning dataset in the overhead line area is available. This study is useful for electric power suppliers because it provides valuable information about the most lightning-prone sections of overhead power lines. The method can also be beneficial to people selecting the optimal route (least amount of lightning strikes) for power transmission lines based on lightning density.