Use this excel spreadsheet to generate the textural fragment modifier based on percentages of fragments and parafragments. This calculator is from the National Soil Survey Handbook Part 618, Subpart B, Exhibit 618.90.
Soil Texture Calculator
Input sand and clay percentages to obtain the soil texture.
SPAW Soil Water Characteristics
Simulate soil water tension, conductivity, and water holding capability based on the soil texture with adjustments to account for gravel content, compaction, salinity, and organic matter.