This paper presents a novel approach to demand forecasting for both crude oil and natural gas : it can be applied with confidence for any country that is politically and economically stable. However, because of these uncertainties and social factors, it is often difficult to formulate a wise policy concerning long-term energy requirements. None the less, there is a need for each country to formulate a sustainable energy strategy. Thus it is desirable to be able to predict accurately future demand requirements for crude oil and natural gas, and so a mathematical model has been developed that can be used with readily-available standard data : it is referred to as the ’modified logit-function demand model’. It is based on saturation curve extrapolations for the appropriate energy intensity (i.e. fuel consumption/GDP), population and GDP/capita. When new input data become available, revised and hence improved projected-demand estimates can be derived readily.