ABSTRACT Residual soils referring to the soils weathered from rocks widely exist all over the world especially in the tropical regions. This paper presents a comprehensive study on variability and estimation of compressibility of Bukit Timah Granitic (BTG) residual soils in Singapore using a database from about 178 Oedometer tests in a site investigation. The statistical analysis shows that the data from the four sites in BTG formation are of no distinct difference and their distribution approximately follow the lognormal type. According to the established transformation models using the database above, the uncertainty was estimated via the first-order estimate, the confidence interval and the estimation interval approaches. The uncertainty of the compression index under different soil states and weathering grades was evaluated. A BPNN model was applied to estimate Cc, and the relative importance of each input attribute is also presented.