Gravel Roadway Cross Section Calculator

Calculator Inputs

Project Name

Road Length (m)

Finished Top Width (m)

Edge Thickness (m)

Crown Rise at Center (m)

Side Slope Ratio (H:1V)

Compacted Density (kg/m³)

Compaction Factor

Wastage Allowance (%)

Truck Capacity (t/truck)

Cost Per Ton

Enter compacted design values for width and thickness. Use a compaction factor above 1.00 when your supplier quotes loose delivered volume.

Reset

Plotly Graph

The chart below shows the roadway gravel cross section generated from your submitted dimensions.

Formula Used

This calculator treats the gravel roadway as a crowned section with a constant edge thickness and equal side slopes on both sides.

Center Thickness = Edge Thickness + Crown Rise
Bottom Width = Top Width + 2 × Side Slope × Edge Thickness
Rectangular Area = Top Width × Edge Thickness
Crown Area = (Top Width × Crown Rise) ÷ 2
Total Side Area = Side Slope × Edge Thickness²
Cross-Section Area = Rectangular Area + Crown Area + Total Side Area
Compacted Volume = Cross-Section Area × Road Length
Loose Volume = Compacted Volume × Compaction Factor
Order Volume = Loose Volume × (1 + Wastage % ÷ 100)
Tonnage = Compacted Volume × Density ÷ 1000

Use the compacted density for tonnage. Use the compaction factor only to estimate how much loose gravel should be ordered for placement.

How to Use This Calculator

Enter the roadway length to be surfaced with gravel.
Provide the finished top width of the roadway section.
Enter the edge thickness and extra crown rise at the centerline.
Set the side slope ratio in horizontal to one vertical form.
Input compacted material density and the loose-to-compacted factor.
Add wastage, truck capacity, and cost per ton if needed.
Press the calculate button to display results above the form.
Review the table, graph, and export options for documentation.

Example Data Table

Scenario	Length (m)	Top Width (m)	Edge Thickness (m)	Crown Rise (m)	Side Slope	Area (m²)	Compacted Volume (m³)	Tonnage (t)
Access road example	250	5.50	0.15	0.04	1.50:1	0.969	242.19	508.59

FAQs

1. What does this calculator estimate?

It estimates gravel roadway cross-section area, compacted volume, loose delivery volume, tonnage, truckloads, and optional material cost from standard roadway section inputs.

2. Why is crown rise entered separately?

Crown rise represents the extra depth at the centerline above the edge thickness. It affects drainage shape, center thickness, and the final cross-sectional area.

3. What does the side slope ratio mean?

A side slope of 1.5 means the gravel side face runs 1.5 units horizontally for every 1 unit vertically. Larger values create flatter side edges.

4. Should density be loose or compacted?

Use compacted density for tonnage because the section geometry is based on the finished roadway. Use the compaction factor to convert that volume into loose supply volume.

5. Why is compaction factor usually greater than one?

Loose gravel occupies more volume before rolling and compaction. A factor above one increases the order quantity so the finished compacted section is achieved on site.

6. How accurate are the truckload results?

Truckloads are planning estimates only. Real deliveries vary with legal payload limits, moisture, material gradation, and how fully each truck is loaded.

7. Can I use it for multiple gravel layers?

Yes. Calculate each layer separately using its own thickness, density, and compaction factor, then add the results for total project quantities.

8. What if my roadway has super-elevation or uneven sides?

Break the road into smaller representative sections. Run separate calculations for each section, then combine the volumes and tonnage for a better estimate.