The analysis of soils by particle size provides a useful engineering classification system from which a considerable amount of empirical data can be obtained. Two separate and different procedures are used. Sieving is used for gravel and sand size particles and sedimentation procedures are used for the finer soils.

For soil containing a range of coarse and fine particles it is usual to employ a composite test of sieving and sedimentation procedures. The Sand Equivalent Test serves as a rapid field test to show the relative proportions of clay-like or plastic fines and dusts in granular soils and fine aggregates.