Calculate gravel base course volume, weight, and truck loads for road construction and haul roads.
Enter road dimensions to calculate how much granular base material you need.
Compaction factor accounts for loose-to-compacted volume change. Order this amount — it will compact down to your design thickness.
A typical unpaved road cross-section (from bottom to top): subgrade (native soil), subbase (pit run or Granular B), base course (Granular A or crushed gravel), and wearing course (sometimes a thin granular cap or chip seal). Each layer distributes load to the one below it.
Soft or wet subgrade requires more base thickness to prevent pumping and rutting. In northern climates, frost penetration depth also drives base thickness requirements.
Granular A is a well-graded crushed aggregate (MTO spec) with fines that bind together under compaction — it's the standard base course for Ontario roads. Granular B is a coarser, less refined material used as subbase. Pit run is unprocessed gravel direct from the pit — cheapest, but variable quality.
Granular material arrives loose and compacts 8–12% under a vibratory roller. A 10% compaction factor is standard. If you need 100 cy of compacted base, order 110 cy of loose material. Always verify your supplier's swell/shrink data for the specific material.
Temporary haul roads for scrapers or articulated trucks typically use 8"–12" of granular base on a prepared subgrade. Geotextile fabric under the base extends road life significantly on soft ground and reduces base thickness requirements.
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