Triangular classification of U.S. public road administration is a commonly used system for textural classification.

The purpose of soil classification is to arrange various types of soils in to groups according to their engineering or agricultural properties.

Since the textural classification is based on the percentages of sand, silt, and clay size making up the soil. Such a classification is more suitable for describing coarse-grained soil.

As group index is a mean of rating the value of soil as a sub-grade material. It can be used for finding the performance and quality of the soil.

Terms such as gravel, sand, silt, and clay are used to indicate grain sizes. These terms are used only as a designation of particle size.

Indian standard classification (IS: 1948-1970) is based on the M.I.T. system.

Since properties of clay soils is less dependent on particle size distrubution(textural classification) and more dependent on size it is best suited for clay soil.

A triangle, having equal length of sides (i.e. Equilateral triangle) is used in textural classification chart.

HRB classification system, also known as public road administration (PRA) is based on both the particle-size composition and plasticity characteristics.

Based on particle size, soil can be classified as