It has previously been shown that the entanglement molecular weight (M-e) and the plateau modulus (G(N)(0)) of flexible polymers can be correlated to the unperturbed chain dimension, (0)/M, chain density (rho) via the use of the packing length (rho), which is defined as the volume of a chain divided by its mean square end to end distance. For polyolefins and co-polyolefins where (0)/M remains unmeasured a method is presented herein where knowledge of the average molecular weight per backbone bond (m(b)) allows G(N)(0) and thus M-e to be estimated. This is particularly valuable for the case of polyolefin copolymers where the melt chain dimensions (and thus the packing length) are unknown.