This video clearly explains the procedure for the Relative Density of Cohesionless Soils | Minimum and Maximum Dry Density of Cohesionless Soils.
Relative density is defined as the ratio of difference of void ratios of cohesionless soil in its loosest state and the natural state (emax - e) to the difference between void ratio in its loosest and densest state (emax - emin). Relative density determines the compactness of the cohesionless soil.