The micro-segregation picture of a block copolymer was applied to a low molecular weight liquid crystal (LC) to clarify the similarities between them with respect to structured mesophase formation. Calamitic LC molecules were regarded as block compounds composed of a rigid anisometric core terminated by flexible chains. Then, the incompatibility parameter Xcore-chain and volume fraction f(core) were considered analogous to X-AB and f(A) in A-B diblock copolymers. Fedors's method, which was originally used for polymers, was utilized to estimate Xcore-chain and f(core). We found good correspondence in the X versus f phase diagram between block copolymers and block LCs.