Understanding Gravel Driveway Calculations
The core material is ordered by **Volume** in **Cubic Yards** (Cu. Yd.). The calculation is based on the simple volume of the area. The total cost is the sum of the material cost and the labor cost, calculated per square foot of area.
Volume and Material Calculation
The volume calculation follows the standard formula: $$\text{Volume (yd}^3) = \frac{\text{Length (ft)} \times \text{Width (ft)} \times \text{Depth (in)} / 12}{27}$$ The recommended volume includes a **15% contingency** factor. This high factor accounts for: **1)** Compaction during rolling (a 6-inch layer may compact down to 5 inches), **2)** Loss due to mixing with the sub-base, and **3)** Waste along the edges.
Installation Cost Components
Material Cost ($/Cu. Yd)
- **Base Gravel (Sub-Base):** Cheaper, typically larger, angular crushed stone like 2- to 3-inch road mix or recycled concrete aggregate (RCA).
- **Top Coat (Surface):** More expensive, finer, and often decorative gravel (e.g., pea gravel, crushed limestone, 3/4" fractured stone).
- **Delivery Fees:** Hauling costs can significantly impact the final price, especially for small orders.
Labor Rate ($/Sq. Ft)
- **Includes:** Excavation/grading of the existing surface, installation of a **geotextile fabric** (highly recommended for gravel driveways), material spreading, and **compaction**.
- **Variables:** The rate can vary widely based on the amount of site preparation required (e.g., tree removal, heavy grading).
Note on Multi-Layer Driveways:
For best performance, driveways should use **multiple layers** of different gravel sizes (large base, medium binder, small surface). For multi-layer projects, calculate the volume separately for each depth and add the totals together before ordering.