Decomposed Granite Calculator estimates DG order quantity with area×depth×(1+compaction%)×(1+waste%)×density, showing tons, loose volume, mass per area, and delivery volume.
Ordering decomposed granite for a landscape surface demands an accurate material quantity that accounts for the dramatic volume loss during mechanical compaction and for trimming waste at the edges.
A Decomposed Granite Calculator uses the compacted depth, the area dimensions, the stone’s loose bulk density, a compaction factor, and a waste margin to determine the total uncompacted mass in tons.
Compaction Behavior and Loose Density of Decomposed Granite
Decomposed granite, a blend of crushed stone and fines, is placed in a loose state and then compacted with a vibratory plate. The material can lose 25 to 35 percent of its original loose volume as the particles lock together and air voids collapse. Without accounting for this shrinkage, a project will run short by a quarter to a third of the anticipated volume.
Loose bulk density typically ranges from 95 to 115 pounds per cubic foot for standard 3/8‑inch minus decomposed granite. The in‑place compacted density rises to roughly 120 to 135 pcf, but the order‑mass calculation uses the loose density because the material is weighed and delivered in its uncompacted state. A mid‑range loose density of 105 pcf appears as the default in many estimating guides.
The waste margin covers material lost to edge spillage, uneven subgrade, and unavoidable scatter during spreading. It is applied as a percentage increase over the already‑compacted loose volume and has no direct relationship to compaction itself. Both factors multiply the net compacted volume to produce the gross loose volume that must be ordered.
How the Decomposed Granite Calculator Computes Loose Volume and Mass
The computation multiplies the plan area by the compacted depth, then scales up by the compaction and waste multipliers to arrive at the loose volume. Mass is found by multiplying that loose volume by the loose bulk density of the stone.
Gross Loose Volume (ft³) = L × W × (D / 12) × (1 + C/100) × (1 + W/100)
L = Length of the area in feet
W = Width of the area in feet
D = Desired compacted depth in inches
C = Compaction factor as a percentage (default 30)
W = Volumetric waste margin as a percentage (default 10)
Order Mass (lb) = Gross Loose Volume (ft³) × Loose Density (lb/ft³)
Order Mass (tons) = Order Mass (lb) / 2,000
For metric entries, length and width are taken in meters, depth in millimeters, and density in kg/m³. The logic converts meters to feet and millimeters to inches internally, computes the mass in pounds, then converts to kilograms and tonnes for display. The underlying sequence of multipliers remains identical.
Worked Example: 100‑Square‑Foot Pathway with a 2‑Inch Compacted Depth
Area equals 10 ft × 10 ft, or 100 ft². Net compacted volume is 100 ft² × (2 in / 12 in per ft), which gives 16.67 ft³.
Loose volume needed before waste multiplies the compacted volume by the compaction factor. With a 30‑percent factor, 16.67 ft³ × 1.30 yields 21.67 ft³.
Gross loose volume including waste applies an additional 10‑percent margin. Multiplying 21.67 ft³ × 1.10 results in 23.83 ft³ of loose decomposed granite required.
Order mass converts volume to weight using the 105 pcf loose density. 23.83 ft³ × 105 lb/ft³ equals 2,502.5 lb.
Dividing by 2,000 pounds per short ton gives the final order quantity. 2,502.5 lb / 2,000 = 1.25 tons, matching the default output.
Loose depth with waste, a visual check for site crews, is the gross loose volume divided by the area then converted to inches. 23.83 ft³ / 100 ft² × 12 in/ft = 2.86 inches of loose material before any compaction.
Coverage per ton works out to 100 ft² / 1.25 tons, or 79.92 ft² per ton. Delivery volume equals gross loose cubic feet divided by 27: 23.83 ft³ / 27 = 0.88 yd³. That loose yardage fills 88 percent of a 1‑cubic‑yard truck bed, a useful constraint when scheduling deliveries.
Selecting an Appropriate Compaction Factor and Waste Margin
Compaction factor for decomposed granite compacted in 2‑ to 3‑inch lifts with a vibratory plate commonly falls between 25 and 35 percent. Material with a higher proportion of coarse aggregate and fewer fines tends toward the lower end because the particle skeleton resists further densification.
Very dry stone or specifications demanding an exceptionally dense surface can push the factor toward 35 percent. Field tests with a nuclear density gauge often record dry densities above 120 pcf, confirming that a 30‑percent factor reliably models the volume reduction for most well‑graded decomposed granite.
Waste margin depends on the shape and edge conditions of the installation. A rectangular path with restrained edges, such as steel or paver borders, may need only 5 percent.
Curving beds, irregular flagstone joints, or areas with many penetrations raise the margin to 10 or 15 percent. The default 10 percent covers typical residential patios and pathways where some trimming is unavoidable but major recuts are not expected. Excessively low waste assumptions lead to a short load, while overly conservative margins inflate cost and leftover material.
Density Ranges and Material Variability
Loose density is not a fixed number; it varies by source quarry, gradation, and moisture content. Standard decomposed granite from California and Southwest quarries usually tests between 100 and 110 pcf when dry and loosely piled. Stabilized products containing a small fraction of organic binder or cementitious additive may weigh 110 to 115 pcf loose.
If the supplier provides a certified loose density, substituting that value yields a more precise order mass than relying on a generic average. A 10‑pcf shift in assumed density changes the tonnage for this 100‑ft² example by about 0.12 tons, a difference that grows with project size.
Site moisture can temporarily increase the as‑delivered weight without changing the solid volume, because water fills part of the void space. Bulk‑density measurements should reference oven‑dry weight to avoid ordering by a water‑inflated mass that will lose weight as the material dries. Contractors who base orders on a load ticket weight should confirm the quarry’s reported moisture content.
From Mass to Truckloads: Delivery Volume and Coverage Estimates
Loose cubic yardage determines whether a single‑axle dump truck, a trailer, or multiple trips are necessary. A typical residential decomposed granite order of 2 to 3 tons occupies 1.5 to 2.2 loose cubic yards.
At a volume‑per‑ton rate of 0.71 yd³ per ton, a 5‑ton load would require about 3.55 yd³ of truck capacity, well within the 5‑ to 6‑yard bed of a small dump truck. Checking the truck‑fill percentage prevents over‑ordering beyond the hauler’s legal payload.
Coverage per ton drops sharply as compacted depth increases. At 2 inches, 1 ton covers roughly 80 ft². At 3 inches, coverage falls to approximately 53 ft² per ton, and at 4 inches it reaches about 40 ft² per ton for the same density and compaction assumptions. These figures use the same formula with depth as the only changed variable, offering a direct scaling rule for estimators.
Rapid field checks compare the loose depth before compaction with the calculated loose‑with‑waste value to verify that the spread crew is placing the right amount of material before running a compactor.