Rock mass soundness is typically measured by engineers using the rock quality designation (RQD) combined with their own experience (Choi and Park 2004). Many researchers have established empirical models to estimate mechanical properties from the RQD (Zhang and Einstein 2004; Jiang et al. 2009), rock mass rating (RMR) (Bieniawski 1978; Nicholson and Bieniawski 1990; Chun et al 2009; Hoek and Brown 1997), or Q methods (Barton et al. 1974; Barton 1983, 2002) and the cumulative core index (Sen 1990). Considering its worldwide acceptance and usage in major rock mass classifications such as Q and RMR, RQD is among the practical useful parameters, especially when the geological strength index (GSI) is concluded from the RMR. Applications of RQD have also been quickly extended to other areas of rock mechanics, so that it is now among the fundamental parameters of geotechnical engineering (Hoek and Brown 1980; Hoek and Bray 1981). The RQD index is affected by a number of well-known factors and limitations; For example, it yields different values for a given location when samples are extracted from cores with different drilling orientations. Moreover, factors such as the quality of drilling and logging, rock strength and core size, water conditions, joint apertures, alteration, and roughness affect RQD values. Another significant limitation of the RQD definition is its dependence on the selected threshold length of unbroken rocks (Priest and Hudson 1976; Harrison 1999; Hack 2002; Chen et al. 2005). Therefore, RQD values for the same core typically vary for different threshold lengths. In practice, a familiar observation associated with this drawback is that RQD values tend to be either high or low (often above 70 % or below 10–20 %) in most rock engineering projects. Some values (e.g., between 40 and 60 %) are less frequently encountered, due to the customarily and universally adopted, but very arbitrarily selected, threshold value of 10 cm (for NX cores) in the assessment of RQD (Harrison 1999). To obtain a wider range of RQD values, Harrison (1999) proposed a technique for determining the optimal threshold length. However, this approach is only appropriate for a particular rock mass. Besides, this technique requires the determination of the minimum and maximum values of the discontinuity frequency in the rock mass, which generally means that the simplicity of the original RQD is lost. It is concluded that, since RQD measurements are encumbered by several limitations, they should be used with caution. Limitations of the RQD index influence engineering results when applied in classification systems, numerical modeling, and other engineering assessments (Palmstrom, 2005). Thiswork aims to describe the deficiencies of the RQD and propose a new, straightforward method for calculation of borehole RQD. This method also enables removal of the effect of joint orientation and piece length on RQD values.