Soil Texture Calculator

How to read the USDA soil texture triangle

The USDA texture triangle groups mineral soil by the proportions of sand, silt, and clay. Each side represents a percentage, and the three values must total 100. Follow the line for each percentage into the triangle; their intersection identifies the texture class. A loam has a useful mixture of sizes, but it does not contain equal thirds. The calculator helps place your measurements in the classification.

Use percentages or individual layer heights

If your report gives percentages, select percent for each input and enter the reported sand, silt, and clay values. For a jar estimate, enter the thickness of each separate layer using consistent units. The silt input is the silt layer alone, not the combined sand and silt height. Record the original readings so you can spot a measurement error and repeat the test.

A mason jar test at home

Collect a representative mineral soil sample, remove stones and large plant debris, and use a straight-sided clear jar. Add soil and water, leaving room to shake. Mix thoroughly, then place the jar on a level surface. As a rough observation schedule, mark settled sand after about one minute, the next layer after two hours, and the final fine layer after 48 hours. Measure the individual layers and divide each thickness by their total.

Clumps, organic matter, fine sand, and poorly dispersed clay can make a jar estimate inaccurate. Some particles remain suspended beyond the observation period. Treat the result as a starting point for field observations, especially near a texture-class boundary. The procedure is adapted from Clemson Extension's jar test guide; laboratory methods control dispersion and settling more closely.

Texture, water retention, and nutrient holding

Sandy soils often drain quickly, while finer soils can retain more water. Actual drainage also depends on structure, compaction, depth, and layers below the surface. Clay mineral type and organic matter influence cation exchange capacity, or CEC, which relates to the retention of positively charged nutrients. Texture alone cannot supply a CEC value or tell you how much fertilizer to apply.

Use small, well-timed irrigation checks to learn how your own soil behaves. Improve structure through suitable organic inputs and avoid working wet soil. For measured chemistry or particle size, compare soil testing options. The USDA texture calculator provides an additional reference for percentage-based classifications.

Frequently asked questions