In this paper, two developed models for electrical conductivity of polymer nanocomposites are linked to express an equation for tunneling distance between adjacent carbon nanotubes (CNT) by the effective properties of polymer matrix, CNT, interphase and networks. The tunneling distance is calculated for some samples at different CNT concentrations. In addition, the suggested equation is applied to justify the impacts of all parameters on the tunneling distance. The tunneling distance decreases as CNT concentration increases, but its variation reduces at high CNT loading. The suggested equation demonstrates that a thick interphase, thin and short CNT, high filler concentration, poor percolation threshold, low surface energy of polymer and high CNT surface energy produce a short tunneling distance.