How to use this calculator
Enter the area and layer depth, then ask your supplier for the bulk density appropriate to the material and state you are ordering. Add an explicit volume allowance only if your project requires it. Choose the stock-and-bags option when buying bagged material, then enter usable stock and the net mass stated for one supplier bag. There is no assumed bag size. The large result is the total project requirement; the purchase rows show only the new bags needed. Use the unit selector for metric quantities.
The formula
A worked example
A 20 × 10 ft area at 6 inches deep is 100 cubic feet, or 3.7037 cubic yards. At an entered 100 lb per cubic foot and no extra allowance, it weighs 10,000 lb: 5 U.S. short tons. In metric units, 2 × 3 m at 5 cm deep is 0.3 m³. At an entered 1,600 kg/m³ density it requires 480 kg. With 30 kg already available and supplier bags of 25 kg, buy 18 bags and leave no surplus against the plan. At 5.1 cm depth, the requirement is 489.6 kg: buy 19 bags and retain 15.4 kg.
Assumptions & limitations
Density varies with aggregate type, size distribution, moisture, and compaction. The default is an example. Stock, new bags and the estimated requirement must describe the same compatible material on a comparable mass and moisture basis. Enter net contents, not packaging weight or a nominal bag volume. The allowance applies to the project requirement before stock is deducted. Loose and compacted volumes are not interchangeable; this tool does not choose a compaction factor or pavement design. Leftover is relative to the estimate, not a guaranteed real-world yield.
Common questions
Are short tons and metric tonnes the same?
No. A U.S. short ton is 2,000 lb; a metric tonne is 1,000 kg. The selected output explicitly names the unit.
Does changing density change volume?
No. The geometric volume depends on dimensions. Density changes the estimated mass of that volume.
Does the large weight result tell me what to buy?
It shows the total project requirement. In bag-order mode, read Whole bags to buy and New purchase weight after subtracting your usable stock.
Can I enter any bulk bag as one tonne?
No. Use the supplier’s stated net mass for that specific bag. Bag labels and contents vary, and a volume-only label is not a mass measurement.
What if I already have enough gravel?
The purchase count is zero. The calculator shows the stock expected to remain after the planned fill; it does not add another allowance to the existing stock.
Supporting reference
The method above states this calculator’s assumptions. This reference provides related definitions and technical context.
Vulcan Materials: construction aggregate estimator ↗Formula and worked example checked against automated test cases. About our methodology.