Tilth is a qualitative term that describes the physical state of soil. There is need for a quantitative understanding of soil tilth to help scientists, engineers, and farmers better understand how to manage soil. A “tilth index” based upon five soil physical properties was developed to quantify tilth. Values of bulk density, cone index, aggregate uniformity coefficient, organic matter content, and plasticity index were used to calculate an index, that ranges from zero for conditions unusable by the plant to one for a soil that is nonlimiting for plant growth.