The hydraulic conductivity is a parameter in geotechnical engineering practice that is key in seepage and consolidation analysis. Experimental results show that the hydraulic conductivity is mainly governed by the soil porosity, and correlations with void ratio are usually proposed. The validity of these correlations has been verified for soft clays and sands; however, few studies have included stiff clays. In this work, the hydraulic conductivity of Boom clay, a stiff clay taken from the Essen site in Belgium, was determined from both consolidation and constant-head percolation tests. The data obtained was then analyzed to evaluate the existing correlations to predict the hydraulic conductivity. In addition, as these correlations usually require a referred hydraulic conductivity at a known void ratio, the existing methods are often difficult to use in practice. Thus, a new method was developed allowing the prediction of hydraulic conductivity without the referred value, which was based on two existing correlations and involved the void ratio and the liquid limit. The proposed correlation was verified using the experimental results obtained from Boom clay samples that were collected from various locations in Belgium.