A simple expression has been found relating the relaxation spectrum and nonlinear shear rate dependent viscosity. In this expression the value of the relaxation spectrum is the product of one‐half the shear stress and the slope of the steady flow curve at a relaxation time twice the value of the inverse shear rate. This relation was applied to a set of linear polyethylene melts and found to agree quite well with relaxation spectra obtained from linear viscoelastic quantities. A comparison with a similar equation relating the relaxation spectrum with loss modulus was shown to lead to a transformation between steady‐state viscosity and dynamic viscosity. Similar relations have been found in the literature.