Abstract: A method for calculating areas of farmable land for the working of agricultural machinery, applied in an electronic device, obtains data as to specific locations and data as to time-points of agricultural machinery within a time period when working normally, and processes and cleans the data time-point data to remove data of location and time-points which are time-point data not in a normal operation state because of repeated traverses and time spent in non-operating states. The electronic device clusters and segments the location and time-points data and time-point data distinguishes between time-point data of the agricultural machinery in a normal operation state and data in non-operating or repeating states. The location and time-points time-point data of the agricultural machinery in the normal operation state are retained. The electronic device generates polygons based on the retained time-point data and calculates operable areas according to the polygons.