Gravel coverage changes when the installed depth changes. Use a coverage chart to check a delivery or compare project sections after confirming that the volume and depth use compatible units.
How much area does gravel cover?
Coverage decreases as depth increases. Coverage area equals volume divided by depth, provided both values use compatible units.
The cubic-yard and cubic-metre tables use geometry alone. Coverage by ton requires the selected product's bulk density and material condition, so the tables stay volume-based.
Coverage formula
Coverage area = material volume ÷ installed depth
A coverage table is a geometry reference. Delivered and compacted yield also depend on the product and material state. The placed depth must be measured consistently, and the ordered material may settle, compact, spill, or vary across the surface.
Coverage from one cubic yard
One cubic yard contains 27 cubic feet. Converting depth from inches to feet gives the following mathematical coverage:
| Installed depth | Calculated coverage |
|---|---|
| 1 in | 324 ft² |
| 2 in | 162 ft² |
| 3 in | 108 ft² |
| 4 in | 81 ft² |
| 6 in | 54 ft² |
Example at 3 inches: 27 ft³ ÷ 0.25 ft = 108 ft².
Coverage from one cubic metre
| Installed depth | Calculated coverage |
|---|---|
| 25 mm | 40 m² |
| 50 mm | 20 m² |
| 75 mm | 13.33 m² |
| 100 mm | 10 m² |
Example at 50 mm: 1 m³ ÷ 0.05 m = 20 m².
See how depth changes coverage
Coverage changes in inverse proportion to depth when volume stays fixed. Doubling the depth halves the covered area. Increasing depth by 10% leaves 1 ÷ 1.10 = 90.91% of the original coverage.
One cubic yard covers 108 ft² at 3 in. At 3.5 in, the same volume covers 27 ÷ (3.5 ÷ 12) = 92.57 ft². The extra half inch reduces the mathematical coverage by 15.43 ft², or about 14.29%.
This sensitivity explains why several field depth readings matter. It does not set a construction tolerance. Use the project requirement to establish the permitted depth range, then calculate the material effect of measured variation.
Reverse the calculation
If the area and depth are known, reverse the table to calculate required volume:
Required volume = area × installed depth
For a 450 ft² area at 2 inches, first convert depth to feet: 2 ÷ 12 = 0.1667 ft. The volume is approximately 75 ft³, or 75 ÷ 27 = 2.78 yd³. Keep more precision during the calculation and round only the planning result.
For a 32 m² area at 75 mm, convert depth to 0.075 m. The volume is 32 × 0.075 = 2.40 m³.
How to use the table
- Confirm the required installed depth for the project.
- Measure the net area, including separate strips or widened sections.
- Divide the project area by the table coverage to estimate cubic yards or cubic metres.
- Use the direct formula for a depth missing from the table and retain calculation precision.
- Discuss compaction, settlement, minimum order, and delivery increments with the supplier.
Use a depth that is missing from the table
Calculate an unlisted depth directly from the same formula. Convert the depth into feet or metres first, then divide the available volume by that depth.
Coverage from 1 yd³ = 27 ft³ ÷ depth in feet
At 2.5 in, the depth is 2.5 ÷ 12 = 0.208333 ft. One cubic yard covers 27 ÷ 0.208333 = 129.6 ft² as an even mathematical layer.
Coverage from 1 m³ = 1 m³ ÷ depth in metres
At 60 mm, the depth is 0.06 m. One cubic metre covers 1 ÷ 0.06 = 16.67 m², rounded to two decimals.
Handle a project with changing depth
Split abrupt depth changes into separate areas. Calculate the volume of each section from its own area and required depth, then add the section volumes.
A 200 ft² path at 2 in uses 200 × 2 ÷ 324 = 1.235 yd³. An adjoining 100 ft² pad at 4 in uses 100 × 4 ÷ 324 = 1.235 yd³. Together they require 2.469 yd³ of measured geometric volume before any documented allowance or supplier rounding.
For a depth that changes steadily between two measured ends over a consistent area, an average-depth calculation can describe that linear transition. Ruts, isolated depressions, crowns, and edge tapers need smaller measured sections because one average can conceal local volume.
Separate mathematical coverage from an order
| Quantity stage | What it represents | Controlling information |
|---|---|---|
| Table coverage | An even layer from a stated bulk volume at a stated depth | Compatible units and geometry |
| Measured project volume | Net area multiplied by the required depth for each section | Field measurements and project requirements |
| Planning quantity | Measured volume plus a documented project allowance | Measurement tolerance, placement conditions, settlement, or compaction information |
| Supplier order | Planning quantity adjusted to the quoted selling increment | Product data, minimum order, package yield, delivery terms, and supplier rounding |
Myth and reality: coverage tables answer a narrow question
| Myth | Reality |
|---|---|
| The 3-inch row recommends a suitable project depth. | The row calculates coverage at a depth supplied by the reader. Project documents and qualified guidance determine suitability. |
| One ton has a fixed coverage area. | Ton-based coverage depends on the selected product's bulk density, material condition, and placed depth. |
| Nominal order volume proves finished yield. | Surface variation, material state, placement, settlement, compaction, and handling affect the finished layer. |
| One area total is enough for every site. | Separate sections preserve exclusions, widened areas, and different required depths. |
Record a field coverage check
Use several depth checkpoints across each section and record the measured state at the time of the check. A short field log should include the section name, net area, required depth, actual low and high readings, material state, installed volume to date, and remaining volume.
Recalculate the remaining work when the prepared surface, finished boundary, or required depth changes. Keep the original measurement and revised measurement as separate records so the change can be traced.
Coverage for irregular areas
Use the longest length and widest width only when that full rectangle will receive material. Divide the shape into smaller rectangles, triangles, or measured strips, calculate their areas, and add them. Where the width changes continuously, field measurements at sensible intervals provide a checkable basis for the area total.
Deduct large exclusions such as slabs, planting beds, structures, or drainage features only when they will not receive the selected material. Small deductions may not change the supplier's rounded selling unit, but they should still remain visible in the calculation.
Check placed depth in the field
- Set several check points across the area before spreading.
- Measure from the prepared surface to the finished gravel surface at each point.
- Record low, high, and centre readings across the section.
- Compare the measured state with the design requirement: loose, settled, or compacted.
- Recalculate the remaining volume if the installed depth or finished area changes.
A 3-inch entry means an even 3-inch mathematical layer. The table cannot account for ruts, crossfall, edge taper, surface depressions, or a loose layer that will later compact.
Why real coverage can differ
The tables assume an even mathematical layer. Real projects have surface variation, edges, slopes, wheel tracks, grading tolerance, and handling loss. Loose delivered volume may not equal final compacted or settled volume. Record those differences as explicit project assumptions beside the chart result.
Reverse calculation: volume from area
For U.S. customary units, cubic yards equal area in square feet multiplied by depth in inches, then divided by 324.
Cubic yards = area (ft²) × depth (in) ÷ 324
For 1,000 ft² at 3 in, the geometric volume is 1,000 × 3 ÷ 324 = 9.259 yd³. Keep 9.259 for later allowance and supplier rounding; display 9.26 yd³ for the measured result.
Return to the Gravel hub before selecting a product or applying a project depth.
Common mistakes
- Reading the 2-inch row when the design requires 2 inches after compaction.
- Using the gross site area without deducting buildings or other exclusions.
- Treating a coverage table as a material-selection guide.
- Assuming one cubic yard will always arrive or place as exactly one cubic yard.
Coverage questions
Does stone size change the mathematical table?
The table converts a stated bulk volume into an even layer, and its geometry is independent of stone size. Stone size and gradation can still affect placement, surface finish, voids, settlement, compaction, and whether the chosen depth is suitable.
Should depth mean loose or compacted depth?
Use the state required by the project and label it. If the required result is a compacted layer, the order may need separate allowance or conversion based on project or supplier information. Label the loose delivery volume and compacted design depth as separate material states.
Sources and scope
- NIST Handbook 44 (2026), Appendix C: 27 cubic feet per cubic yard.
Source scope: NIST supports the unit relationship. The coverage rows are derived geometry. Product data and project requirements control yield and the selected depth. Sources and calculations checked 28 July 2026.
