In an integrated noise isolation system, both gasket and bolt isolators play an important role in the resultant total load, contact stress, and system static and dynamic stiffness. One standard approach to design is based on using a shape factor in conjunction with a simple stress-strain relation. This approach can produce reasonable results under small deformation. But the deviation is so large that it is not appropriate to use it for reliable designs under large deformation. Experimental approaches and finite element methods are effective at characterizing the load-deflection relationship of bolt isolators under large compressive deformation. In this paper, a parameter study of a sequence of finite element analyses will be presented and a parametric model will be determined based on the FEA results to best represent the isolator load-deflection behavior under large compression. The resulting formula can be used to quickly and accurately determine the isolator static and dynamic stiffness. The parametric model was compared to experimental measurements with very good agreement.