Decline curves are one of the most extensively used forms of data analysis employed in evaluating gas reserves and predicting future production. The parameters determined from the classical fit of historical data can be used to predict future production. The decline-curve analysis technique is based on the assumption that past production trends and their controlling factors will continue in the future and, therefore, can be extrapolated and described by a mathematical expression. In the present work, simple-to-use predictive tool, which is easier than existing approaches, less complicated with fewer calculations, is formulated to arrive at an appropriate estimation of nominal (initial) decline rate, and the Arps’ decline-curve exponent. The results can be used in follow-up calculations for analysis of past trends of decline in production performance i.e., rate versus time and rate versus cumulative production plots, for wells as well as reservoirs. The proposed simple-to-use approach can be of immense practical value for reservoir engineers and scientists to have a quick analysis on the production decline-curve of past trends of wells and reservoirs for wide range of conditions without the necessity of any field test measurements and/or trials. In particular, petroleum engineers would find the proposed approach to be user friendly involving transparent calculations with no complex expressions for their applications.