Gravel estimates combine volume and density
For a rectangular layer, geometric volume is:
volume = length × width × finished depth
Estimated mass is:
mass = volume × bulk density
The first formula depends on measurements. The second also depends on material properties. Bulk density changes with aggregate type, grading, particle shape, void space, moisture and compaction state, so weight is never a universal conversion from cubic metres or cubic yards.
Metric example
Consider a path 10 metres long, 3 metres wide and 5 centimetres deep. Convert depth to metres:
5 cm = 0.05 m
10 m × 3 m × 0.05 m = 1.50 m³
Adding 10% gives 1.65 cubic metres. At an entered planning density of 1,600 kilograms per cubic metre:
1.65 m³ × 1,600 kg/m³ = 2,640 kg
That is 2.64 metric tonnes. The accuracy of the weight depends directly on whether 1,600 kg/m³ represents the material as supplied.
US customary example
A rectangular area 30 feet by 10 feet at a finished depth of 2 inches has:
30 ft × 10 ft × (2 ÷ 12) ft = 50 ft³
50 ft³ ÷ 27 = 1.8519 yd³
With 10% allowance the order volume is about 2.037 cubic yards. If bulk density is entered as 100 pounds per cubic foot, estimated mass is 5,500 pounds, or 2.75 US short tons.
Finished depth versus loose delivery
Enter the intended compacted finished depth. Aggregate can settle and rearrange under rolling or vibration, reducing its volume as voids change. A truck delivers material in a loose condition, while the completed base is measured after spreading and compaction.
The calculator applies one percentage allowance to the geometric finished volume. That allowance can represent expected compaction, grade variation and handling loss, but only if chosen from relevant supplier or project information. A generic percentage is not a substitute for a specified compaction factor.
Ask the supplier whether pricing and delivery are based on scale weight or volumetric capacity and which density or conversion they use.
Bulk density is not solid rock density
Solid particle density describes the rock itself. Bulk density includes the spaces between particles in a container or stockpile. Gravel contains voids, so bulk density is lower than the density of solid stone.
Well-graded aggregate can pack smaller particles into spaces between larger ones. Uniform rounded gravel may retain more void space. Crushed angular particles interlock differently. Moisture adds mass and can change how fines occupy voids.
For purchasing weight, use a bulk density for the named product in the relevant condition. Do not use the density of granite, limestone or another solid mineral as though a loose truck load had no air spaces.
Density defaults are only planning values
The calculator starts at 1,600 kg/m³ in metric mode and 100 lb/ft³ in US mode. Those are convenient middle-of-the-road planning inputs, not certified properties of every aggregate. Changing density by 15% changes calculated mass by exactly 15% while volume stays the same.
Supplier data, a product specification or previous scale tickets are stronger evidence. When a quote is sold by mass, the supplier’s conversion can be more important than a generic online table.
Metric tonnes and US short tons
The word “ton” is ambiguous internationally. A metric tonne is exactly 1,000 kilograms. A US short ton is exactly 2,000 avoirdupois pounds, equal to approximately 907.18474 kilograms.
1 metric tonne ≈ 1.10231 short tons
1 short ton ≈ 0.907185 metric tonnes
The calculator labels both explicitly. Confirm the unit on every quote, especially when comparing suppliers in different markets.
Cubic yards and cubic metres
One cubic yard equals exactly 27 cubic feet. Based on defined length conversions:
1 yd³ = 0.764554857984 m³
1 m³ ≈ 1.30795 yd³
Volume conversion is stable; material mass is where density uncertainty enters. Two suppliers can agree perfectly about a cubic-yard conversion and still quote different weights for different aggregate products.
Measuring irregular areas
Divide an irregular project into simple non-overlapping rectangles, triangles or other measured shapes. Calculate each volume at its intended depth and add them. A triangular plan area is one-half base times perpendicular height.
For curved paths, use a centreline length multiplied by average width when that approximation is suitable, or break the curve into shorter sections. Measure width at several positions rather than choosing one visually.
Sloped ground requires thought about whether depth is measured vertically or perpendicular to the prepared surface. Follow the project detail and takeoff convention.
Uneven subgrade and grade control
Low areas consume additional aggregate. High areas can leave a layer thinner than intended and should be corrected, not averaged away if minimum thickness matters. Establish grades, prepare the subgrade and take multiple depth checks.
A 10 millimetre error across 100 square metres is one full cubic metre. On large areas, depth control often matters more than tiny improvements in length measurement.
Separate base, subbase, bedding and surface layers because they may use different materials, depths and densities. Do not combine them into one average layer if ordering different products.
Compaction and layer thickness
Compaction equipment and achievable thickness depend on aggregate grading, moisture, layer thickness, support and project requirements. Placing one deep loose layer is not always equivalent to building several controlled lifts.
The quantity calculator does not select equipment or verify compaction. For driveways, foundations, pavements or drainage systems, use the specified aggregate and construction method. Qualified project guidance matters because inadequate base preparation can cause rutting, settlement or drainage failure even when volume is correct.
Driveways and load-bearing surfaces
A driveway is not designed solely by choosing a gravel depth from an online table. Vehicle loads, traffic frequency, subgrade soil, frost, rainfall, drainage, edge support, geotextile use and aggregate gradation all matter.
Different layers serve different functions. A coarse base can distribute load, while a finer surface course provides a tighter finish. The appropriate section is a local design question. Use the calculator only after dimensions and material layers are specified.
Drainage applications
Drainage gravel selection involves particle size, cleanliness, filter compatibility, pipe and outlet design. Void space matters to water storage, but bulk delivery volume is not equal to usable water-storage volume.
For a trench, calculate the trench prism, then consider the volume displaced by pipe only if the project takeoff requires it. Geotextile overlaps and pipe quantities are separate. Drainage performance requires a designed route and outlet, not just enough stone.
Bags, bulk bags and truck loads
Packaged aggregate may state mass, approximate coverage at a depth or bag volume. Use the label for that product. A bulk bag marketed as one tonne is a mass package, not necessarily one cubic metre. Its volume varies with density.
Truck capacity can be limited by legal mass before the body is full, or by volume for a lighter material. Do not divide tonnes by a generic truck number. Ask the supplier about load limits, minimum quantities, access and delivery placement.
Access and safe unloading
Delivery vehicles are heavy and require suitable access, clearance, ground support and turning space. Overhead services, gates, slopes, soft verges and underground structures can restrict where a load can be placed. A calculator cannot determine whether a vehicle can safely enter the site.
Plan stockpile location and material movement. Keep people clear during tipping and follow supplier instructions. Manual handling of bagged material also requires realistic weight and task planning.
Moisture and scale weight
Wet aggregate can weigh more because retained water is included on a scale ticket. Fines can hold more moisture than clean coarse stone. A delivery sold by mass may therefore occupy a different volume across conditions.
This is another reason to avoid treating the displayed weight as exact. It is the entered bulk density multiplied by estimated order volume. The actual delivery mass is measured by the supplier’s process.
A gravel ordering checklist
Before ordering, confirm:
- exact product and grading specified for each layer;
- measured length, width and compacted finished depth;
- prepared grades and allowance for low areas;
- supplier bulk density or mass-to-volume guidance;
- whether the quote uses metric tonnes, short tons, cubic metres or cubic yards;
- expected loose-to-compacted relationship;
- minimum order and truck load limits;
- delivery access, unloading point and stockpile space;
- drainage, separation and compaction requirements;
- separate quantities for base, bedding and surface materials.
Limits of this calculator
This tool models one rectangular layer at uniform depth. It converts volume, adds a percentage allowance and estimates mass from the entered bulk density. It does not design pavement or drainage, predict exact compaction, assess subgrade, select aggregate, calculate curved or sloped geometry automatically, or determine truck capacity.
Use the result as a planning estimate and confirm the exact material, density, sale unit, delivery conditions and construction requirements with the supplier and project professional.