A tool has been developed in order to assist farm designers in planning farmstead layouts for dairy farms in hot climates. A mathematical model was developed. Subsequently, the tool is developed by integrating the mathematical model into an electronic spark map. The spark map (decision tree) specifies the farm dimensions, farm total area, and farm perimeter. Furthermore, it calculates the capital investment and the fixed, variable, and total costs of the farm fence. On the other hand, the mathematical model of the spark map requires some input data, such as the dimensions of the farm buildings and the distances between them. According to these data, the spark map will make calculations and show the output data automatically. Data of 4 dairy farms were used to carry out the model validation. The differences between actual and calculated values were determined, and the standard deviations were calculated. The coefficients of variation were between 5 and 7%.