Volumetric block proportion (VBP) directly affects the strength of geologically complex rocks such as bimrocks (block-in-matrix rocks). Since the direct determination of VBP is difficult in most cases, some prediction methods were suggested. In this study, the VBP of Misis fault breccia, which is a type of bimrock, was determined by image analysis techniques and its predictability from P- and S-wave velocity, and density was investigated. Regression analysis showed that there is no relation between VBP and S-wave velocity. However, there is a weak relation between VBP and P-wave velocity. On the other hand, VBP was strongly correlated with density. It was concluded that P- and S-wave velocity may not be a measure of VBP of breccias. However, density is a good measure of VBP, because the relation between VBP and density is strong and statistically significant.