Stimulated reservoir volumes (SRV) calculated from microseismic-event distributions have been successfully used to establish correlations with the production for tight-oil and -gas reservoirs. Although only applicable in reservoirs where complex fracture networks are created, the calculation of SRV numbers has proven to be a valuable measure of the stimulation effectiveness and, in some circumstances, prediction of the well’s production. It is important to note that, while SRV is an important baseline measurement of the total rock volume affected by the stimulation, other factors, such as the density and conductivity of fractures within the SRV, are just as important for well performance. Calculating SRV from microseismic-event distributions often involves "shrink-wrapping" the event locations without any consideration of the location uncertainty of the individual event. Not just the amount of location uncertainty, but the directionality of the nonuniform uncertainty space as well as its definition impact the calculated SRV number. Other impacts are the radiation pattern, viewing distance, and accuracy of the underlying velocity model. In this paper, the quantitative impact of these factors on the SRV number is discussed and the developed methodology is applied to several datasets, resulting in the calculation of uncertainty bars for the SRV number. These SRV uncertainty ranges help explain some of the anomalous deviations of the SRV number in individual projects from the general trend in a certain area, which is demonstrated using an example from the Barnett shale.