How to Calculate River Rock Quantity
River rock (or landscape aggregate) is typically sold by **weight** (Tons or tonnes/kg). The calculation involves finding the volume of the area to be filled and multiplying it by the rock's bulk density.
Calculation Formula
The fundamental principle is: **Weight = Volume × Density**.
- **Volume:** Length $\times$ Width $\times$ Thickness (Ensure all units are consistent, e.g., meters or feet).
- **Density:** Bulk density of the rock type (kg/m³ or lb/$\text{ft}^3$), which accounts for the air voids between the round rocks.
- **Waste:** Add an extra **5-10%** to the final weight to account for settling, uneven base, and spillage.
Bulk Density Estimates
Bulk density varies significantly; **always confirm the exact figure with your local supplier.**
| Material | Approx. Density ($\text{kg}/\text{m}^3$) | Approx. Density ($\text{Tons}/\text{yd}^3$) |
|---|---|---|
| Standard River Rock | ~1400–1500 $\text{kg}/\text{m}^3$ | ~1.2–1.3 $\text{Tons}/\text{yd}^3$ |
| Pea Gravel (small) | ~1600–1700 $\text{kg}/\text{m}^3$ | ~1.3–1.4 $\text{Tons}/\text{yd}^3$ |