The work is devoted to the determination of the actual errors in the estimation of reserves for explored gold deposits. To calculate them, an algorithm is proposed, based on the analysis of the characteristics of the variability of the content of the component in exploration samples. The estimation of the error was carried out for category C1 reserves. Research results show that the relative standard error definitions middle contents in blocks, comparable productivity of the enterprise, for large and medium-sized deposits is 10- 15%; for small objects, it can increase up to 30%.Values allowed evidence-based errors can be used to selection of parameters of the exploration network and qualification of reserves on a quantitative basis.
Key words: variability of grades, categories of reserves, error estimates, annual productivity.