At present, when estimating the state of the resource base and the general forecast for the development of oil production, ones often operate with the reserves-to-production ratio, which reflects, as it is believed, a guaranteed time for involving current recoverable reserves in active development. However, the terms (numbers) differ significantly. In this regard, it seems appropriate to once again discuss the content of the commonly used ratio, the differences in approaches to its estimation and use in Russia and abroad, as well as the possibility of using it when forecasting production and the need for an increase in reserves.