Maximum dry unit weight, ${gamma}_{dmax}$, is the most important engineering properties for subgrade soil. Existing models to predict ${gamma}_{dmax}$ containing many parameters, seem to be rather complex. This paper presents new simple models to predict ${gamma}_{dmax}$. for sandy soils, A number of sieve analysis and compaction tests for 36 types of sands were conducted to develop the regression-based models. Parameters used to estimate ${gamma}_{dmax}$ are both the geometric mean and geometric standard deviation of the soils, or the particle-size distribution curve parameters. Maximum dry unit weights predicted by the models are in good agreement with the laboratory measurements for the soil samples obtained at 16 locations within the Korea.