How the stockpile volume is calculated
Loose material dropped from a conveyor or loader forms a cone. Its slope is the angle of repose, which depends on the material. From the base width and that angle the calculator finds the height and then the volume:
h = r · tan α
Cone: V = π ÷ 3 · r² · h
Ridge pile: V = π ÷ 3 · r² · h + r · h · L
A ridge pile is a long pile with a triangular cross-section and half cones at both ends. Its straight part adds a prism of r · h · L.
Worked example
A cone of dry sand has a base diameter of 20 m and an angle of repose of 35°. Its height is 10 × tan 35° = 7.0 m and its volume π/3 × 100 × 7.0 = 733 m³. At 1.6 t/m³ the pile weighs about 1,170 t. Stretched into a ridge with 30 m of straight length, the same base width holds 2,834 m³.
Typical angles of repose
| Material | Angle of repose |
|---|---|
| Sand, dry | 30° – 35° |
| Sand, moist | 35° – 40° |
| Gravel, rounded | 30° – 35° |
| Crushed stone | 38° – 45° |
| Coal | 35° – 40° |
| Road salt | 30° – 35° |
| Grain | 23° – 28° |
| Wood chips | 40° – 45° |
Values vary with moisture and particle shape. Measure your own pile for accurate inventory.