Soil Texture Triangle Calculator

Soil texture describes the mineral particles smaller than 2 mm, split into three size classes: sand (0.05 to 2 mm), silt (0.002 to 0.05 mm) and clay (smaller than 0.002 mm). Because the three always add up to 100%, any soil is a single point on a triangle, and USDA divides that triangle into 12 texture classes.

This calculator applies the USDA boundary rules directly. For example, soil is sand when silt + 1.5 x clay is under 15, loam when clay is 7 to 27%, silt is 28 to 50% and sand is 52% or less, and clay when clay is at least 40% with no more than 45% sand and under 40% silt. A 40% sand, 40% silt, 20% clay sample is loam; raise clay to 40% and cut sand to 20% and it becomes silty clay.

The most reliable numbers come from a lab particle-size analysis (hydrometer or pipette method), which many state extension soil labs run for a modest fee. A home jar test gives a rough estimate: shake soil with water and a spoonful of dishwasher detergent, then mark the settled layer after about 1 minute (sand), 2 hours (silt) and 24 to 48 hours (clay), and convert each layer's height to a percentage of the total.

Remove gravel, roots and organic matter first, because texture classes only describe the mineral fraction. Lab reports often round, so this tool accepts totals within half a percent of 100 and can rescale a jar test that does not add up exactly.