Sand, Silt and Clay Percentages on the USDA Report Do Not Match Those on the Particle Distribution Report

Have you become concerned because the sand, silt and clay percentages noted on your sample's USDA report are different than the values reported on its particle distribution chart? There's a reason for that: the percentages on the particle distribution chart and those reported on the USDA report are different calculations.

Per the USDA specification, the percentages shown on the textural triangle chart are based only on the portion of the sample passing the #10 sieve, while the percentages shown on the sieve chart reflect the full sample. In fact, this is specifically called out on the USDA report form ("Percentages From Material Passing a #10 Sieve").

Because the USDA results only reflect an artificial sample that has all +#10 material removed (as opposed to the actual physical sample) the two calculations would only produce identical results for samples with 0% retained on the #10 sieve.