Compare a field sample with a laboratory maximum dry density. Use the net wet sample mass, its measured volume, dry-basis water content and the matching lab reference.

Formula: wet density = wet lb ÷ ft³; dry density = wet density ÷ (1 + water content/100); relative compaction = dry density ÷ lab maximum × 100; dry short tons/yd³ = dry lb/ft³ × 27 ÷ 2,000

Worked example

A 12.6 lb wet sample occupying 0.1 ft³ has a wet density of 126 lb/ft³. At 5% dry-basis water content, dry density is 120 lb/ft³. Against a 125 lb/ft³ lab maximum, relative compaction is 96%, with 1.62 dry short tons per compacted cubic yard.

Use compatible field and laboratory measurements

Exclude the container from sample mass. Water content is water mass divided by oven-dry soil mass, not by wet mass. Use a representative sample and the laboratory maximum for the same material and applicable compaction test.

Relative compaction is a ratio

The percentage compares measured dry density with the entered lab maximum. A result over 100% is mathematically possible and should prompt a check of the material, test method and measurements. This tool does not decide whether field work meets a project specification.

Compacted volume is not loose delivery volume

The short-ton conversion describes the dry mass occupying one cubic yard at the calculated field density. It does not predict truckloads, swell, shrinkage or the loose volume to order. Use the bulk-density guide for those distinctions.

Explore the related calculation

For a different starting point, try the bulk density guide or return to the main calculator. Browse the complete tool directory for this site.

Reference and corrections

The definitions and assumptions above follow these sources; the examples and calculator arithmetic are original to this page.

Found a problem? Email contact@cubicyardstotons.org.

Soil compaction calculator

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