Lightning parameters such as ground flash density GFD have been determined using mainly deterministic methods and in the last 20 years the main source of information has been lightning location systems (LLS) data. GFD has some problems like the dependence on the area of the grid studied, strong variations between data in closer points of the grid and its low descriptive capability. Additionally LLS introduce other problems due to the location accuracy that must be in accordance with the area of the grid to be studied. This paper presents a novel fuzzy parameter to calculate ground flash density using modern computational techniques. The new parameter called Fuzzy Ground Flash Density (FGFD) can deal with the problems related to the GFD parameter itself and the location accuracy of the LLS. FGFD gives a better representation of the phenomena and it is more adequate for practical problems especially in engineering subjects such as lightning location systems design and lightning risk assessment. Some examples were created to demonstrate the validity of the new parameter and a real case using the Colombian LLS data is shown.