Molecular dynamics simulation is an important method to predict the shock sensitivity of energetic materials， yet it is computationally expensive and needs to use force fields that may be unavailable. Here， an algorithm was designed and implemented in a computer program in Python for calculating the Steric Hindrance Index （SHI）， which is a descriptor for evaluating shock sensitivity. The algorithm 1） compresses the crystal unit cell of an energetic material keeping the molecular unit rigid to simulate deformation under shock； 2） establishes a new rectangular coordinate system for the specific slip system and rotates the cell to deal with general shock directions and slip systems； 3） assigns molecular units to layers based on the coordinate of their centroid； 4） calculates the overlapped area of each two adjacent layers after projection along the slip direction； and 5） obtains SHI by normalization of overlapped areas. For PETN， BTF， RDX， and TNT at a compression ratio of 0.1， the calculated average SHI are 0.8707， 0.7940， 0.4228， and 0.0924， respectively， which is consistent with the decreasing order of impact sensitivity mentioned in references. SHI classifies the slip systems in line with those based on molecular dynamics simulations， yet with better computing efficiency and methodological applicability.