Slab Foundation Sand Cushion Calculator
Calculate volume and weight of sand or gravel for foundation cushions. Accounts for compaction factor (shrinkage) and converts between Imperial and Metric units.
Volume to Order
Est. Weight
About
A properly compacted sand or gravel cushion is vital for the structural integrity of monolithic slab foundations. It acts as a capillary break to prevent moisture wicking and distributes the load of the concrete evenly to the ground. This estimator calculates the precise material requirements by factoring in the "Compaction Factor" (Load Shrinkage).
When loose sand is tamped down (compacted) to create a solid base, it loses volume. Failing to account for this shrinkage typically results in material shortages of 20-30%. This tool applies a safety margin to ensure you order enough tonnage for the compacted volume required by building codes.
Formulas
Total Order Volume is the Geometric Volume multiplied by the Compaction Factor. Mass is derived from the material density.
Vgeo = L × W × D
Vorder = Vgeo × CF
Mass = Vorder × ρ
Where:
- CF = Compaction Factor (Default 1.25)
- ρ = Density of loose material
Reference Data
| Material Type | Density (Loose) | Density (Compacted) | Compaction Factor |
|---|---|---|---|
| Dry Sand (Fine) | 1,450 kg/m3 | 1,700 kg/m3 | 1.15 - 1.25 |
| Wet Sand | 1,800 kg/m3 | 2,100 kg/m3 | 1.10 - 1.20 |
| Crushed Stone/Gravel | 1,550 kg/m3 | 1,900 kg/m3 | 1.20 |
| Topsoil (Not Rec.) | 1,200 kg/m3 | 1,500 kg/m3 | 1.30 |