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USDA Soil Texture Triangle Calculator

Soil texture describes the relative mass proportions of sand, silt, and clay in the fine-earth fraction of a mineral soil horizon or layer. Under the USDA system, particles larger than 2 millimetres are rock fragments and are described separately rather than included in the three texture percentages. Sand spans 2.0 to 0.05 mm, silt spans 0.05 to 0.002 mm, and clay is finer than 0.002 mm. The sand, silt, and clay percentages must total 100 percent. Their intersection on the USDA textural triangle falls within one of 12 basic classes: sand, loamy sand, sandy loam, loam, silt loam, silt, sandy clay loam, clay loam, silty clay loam, sandy clay, silty clay, or clay. Loam is a region rather than a recipe of equal parts; many different compositions classify as loam. GeoMiner accepts all three percentages, checks the total within one tenth of a percentage point, consistently classifies boundary values, and plots the point on an accessible ternary diagram. A remainder control can calculate silt transparently from entered sand and clay. The result is only as defensible as its sample and measurement. Field texture by feel is an estimate influenced by water content, organic matter, clay mineralogy, aggregation, coarse fragments, and the observer's technique and experience. Laboratory particle-size analysis requires a representative sample, defined horizon and depth, preparation method, dispersion decisions, removal or retention of organic matter or carbonate, a stated measurement method, and appropriate quality control. Report the coarse-fragment content separately and retain the full particle-size distribution rather than only the final class. USDA texture terms are not applicable to every material. Bedrock and cemented horizons, organic soil materials, water or ice, layers dominated by rock fragments or artifacts, and some high-gypsum materials require different descriptors under Soil Survey Manual guidance. Soil texture and soil structure are different properties. Texture alone does not directly determine infiltration, permeability, hydraulic conductivity, water storage, drainage, shrink–swell, erodibility, compaction, trafficability, slope stability, bearing capacity, fertility, contamination transport, or crop suitability. USDA Agricultural Research Service work shows that traditional texture classes can be poor direct predictors of hydrologic response. Structure,

Verification resources

Cross-check terminology, classification, methods, and safety with these authoritative external resources.

  • undefined. The governing National Cooperative Soil Survey guidance for describing soil profiles, properties, horizons, texture, and cases where mineral soil texture terms do not apply.
  • undefined. The USDA textural triangle and its 12 basic sand–silt–clay texture classes, along with field and laboratory description context.
  • undefined. An official public USDA calculator that accepts sand and clay percentages to obtain soil texture and confirms the calculator use case.
  • undefined. Current field-description guidance, particle-size and textural-triangle context, and distinctions between basic texture classes and family particle-size groupings.
  • undefined. Evidence that USDA texture class alone can be a poor predictor of hydrologic response and should not be treated as a direct hydraulic or engineering result.

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Common questions

How do I use the USDA soil texture triangle?
Enter the mass percentages of sand, silt, and clay in the less-than-2-millimetre fine-earth fraction. They must total 100 percent. The intersection falls within one of 12 basic texture classes.
What sizes are sand, silt, and clay in USDA soil texture?
USDA separates use sand from 2.0 to 0.05 mm, silt from 0.05 to 0.002 mm, and clay below 0.002 mm. Rock fragments larger than 2 mm are excluded from the fine-earth texture percentages.
Is loam equal parts sand, silt, and clay?
No. Loam is a region on the USDA triangle, not a 33–33–33 recipe. Several combinations classify as loam, and equal thirds also fall within the loam region.
Can soil texture predict drainage, permeability, or crop suitability?
Not by itself. Structure, bulk density, organic matter, mineralogy, aggregation, pores, compaction, salinity, coarse fragments, horizons, climate, and management also matter. USDA research warns that texture class can be a poor direct predictor of hydrologic response.
Is USDA soil texture the same as USCS engineering soil classification?
No. USDA texture and engineering systems such as USCS use different purposes, boundaries, preparation, and criteria. A USDA triangle result is not a geotechnical classification or design parameter.

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