Neglecting of end effects in rotational viscometry introduces 10-30 % error in the estimate of shear stress sigma (R) at surface of rotating cylindrical spindle. Actual values of the correction coefficient c (L) for a real sensor depend on pseudoplasticity level of a given sample (measured by the flow-behavior index n) and inertia level (measured by the Reynolds number Re). The correction coefficients for the real sensors with coaxial cylinders are calculated by solving the related flow problem for Generalized Newtonian Fluid with power-law viscosity function. In addition to the cylindrical sensors according to ISO 3219 CEN Bruxelles 53:019, (1994) , also some clones with different geometry simplex H = h/R are considered. The results on c (L) (n, Re, H) are presented as a simple empirical formula for easy use in downstream treatment of primary data using the pseudosimilarity approach.