Abstract: It was found that the standard value of the resistance to pile end on a manually dug hole bottom, which was calculated by an empirical formula, is variable, and the variability consists of the uncertainties of the formula itself, pile end diameter and number of heavy-duty DPTs. The calculating formulae were derived according to random field theory and variance propagation law for the variability of the empirical formula itself and the empirical formula considering the self-correlation of the number of DPTs, with the statistical parameter of pile end diameter given. A numerical example showed that the heavy-duty DPT data are suitable to the calculation of correlated distance for the foundations of sand soil and gravelly soil, and each of the number of DPTs correlates to the other one.