Soil resistivity is an important parameter for designing electrical earthing system. The measurement of soil resistivity is greatly influenced by moisture content, temperature, porosity, degree of saturation, number of soil layer(s), and frequency of lightning current. Researchers have proposed various methodologies to provide an approximation of soil resistivity using the listed parameters. In order to ease the process of estimating soil resistivity at a particular area, there is a pressing need to devise a simple tool that enables the calculation of soil resistivity in the most accurate manner. As such, this research proposes a reliable tool for quick evaluation of soil resistivity based on various methodologies using Microsoft Excel’s built-in-functions and Visual Basic Application (VBA) Next, the developed tool was validated using two methods, in which the output value of the calculator was compared with data retrieved from IEEE Std 142-2007 and data reported in past studies. The validation results revealed that the developed calculator may serve as a significant application in future due to its time-saving and cost-effective attributes.