A scheme for the calculation of vertical interblock permeabilities for unsaturated flow in soil was developed and illustrated for one- and two-dimensional unsaturated flows. In the proposed approach, interblock permeabilities were calculated from an average weight of contiguous grid point permeabilities. A large set of exact database weight values was fitted to a highly nonlinear empirical correlation equation as a function of the two contiguous block permeabilities, the dimensionless grid spacing and a soil-dependent parameter. The present scheme was applied to the popular van Genuchten and Brooks and Corey hydraulic functions for relative permeabilities ranging from 10-8 to 1, dimensionless grid spacing ranging from 0.01 to 1, and the soil parameter n of value between 1.05 and 5. The present approach is more accurate than other simple averaging schemes. At the same time the computational effort for the present approach is comparable to that in which the arithmetic and geometric means are used, while enabling to estimate fluxes even with coarse grids.