A correct description of the subsoil is necessary for optimal foundation design and has a practical economic dimension for many geotechnical design problems. Soil strength assessment requires selecting appropriate, standardised tests and validated interpretation methods, based on local research results. However, the correctness of the inference in terms of foundation solutions requires the characterisation of subsoil parameters broken down into units that occur regionally. The article compares the results of shear strength of litho-genetically diverse soils (among others, organic and macroporous, dusty - loess soils) obtained during laboratory and field tests on test plots from the area of Poland. The selected subsoils represent sediments of various lithology, genesis and degree of preconsolidation. The studies included both in situ tests (FVT, CPTU and DMT) and validation laboratory tests. The obtained results made it possible to verify correlation coefficients and formulas, known from the literature, for determining the cu/su parameter obtained by using different methods on a regional basis, as a foundation for determining reliable geotechnical design parameters.