Tonnage Calculator

Bulk material tonnage converts a placed volume into a purchase weight. Length times width times depth in feet gives cubic feet; multiplying by loose bulk density in pounds per cubic foot and dividing by 2000 gives short tons. The density used here is that of the material as delivered and spread, not of its solid particles, so it already embeds the void fraction of the pile: gravel and crushed stone run about 100 to 105 lb per cubic foot (roughly 1.35 to 1.42 tons per cubic yard), sand about 100, fill dirt about 90, topsoil about 75, wood mulch about 25, hot-mix asphalt about 145 and normal-weight concrete about 150. The nearly sixfold spread between mulch and concrete is why the material must be chosen before any tonnage figure is meaningful. Three corrections separate the calculation from the delivery ticket. Moisture is the largest: saturated sand or gravel can weigh 10 to 15 percent more than the same material dry, and the supplier weighs what is actually loaded. Compaction is second - aggregate placed loose and then rolled loses roughly 15 to 25 percent of its volume, so a compacted 4 in base means ordering closer to 5 in of loose material. Third, delivery is quantized by truck: a single-axle dump carries about 5 to 7 tons, a tandem 10 to 14 tons and a tri-axle 15 to 20 tons, with legal axle weight rather than box volume usually the binding limit for dense aggregate. Ordering 5 to 10 percent extra for spreading loss and uneven subgrade is standard practice.

The short ton of 2000 lb is a United States convention that diverged from the British long ton of 2240 lb, which itself descends from the medieval tun, a large wine cask whose loaded weight anchored the unit. The metric tonne of 1000 kg was defined alongside the metric system in revolutionary France in the 1790s and equals about 2204.62 lb, close enough to the long ton to cause persistent confusion in international material contracts and roughly 10 percent heavier than the short ton used in American aggregate pricing. Selling aggregate by weight rather than by volume became standard as certified truck scales and highway construction grew together. Before scales were common, materials were sold by the cubic yard or simply by the load, a practice that survives for mulch and topsoil where low density makes weight-based sale impractical. State highway agencies moved to weight-based payment for aggregate and asphalt during the twentieth century because a ticketed scale weight is auditable while a heaped truck box is not, and because density shifts with moisture and gradation. The Federal Highway Administration and state specifications now define aggregate gradations and the test methods behind them, with ASTM C29 the standard procedure for bulk density and voids in aggregate, which is why supplier quotes come per ton and any conversion to cubic yards depends on a stated density rather than a universal constant.