Inputs
Example data table
| Shape | Size | Depth | Piers | Waste | Total volume | Estimated bags (80 lb) |
|---|---|---|---|---|---|---|
| Cylindrical | 12 in diameter | 4 ft | 6 | 5% | 0.93 yd³ | ~42 |
| Rectangular | 14×14 in | 3 ft | 4 | 7% | 0.68 yd³ | ~31 |
| Cylindrical | 300 mm diameter | 1.2 m | 8 | 6% | 0.81 m³ | ~48 |
Examples are illustrative; always verify site dimensions.
Formula used
- Cylindrical pier volume: V = π × (D/2)² × H
- Rectangular pier volume: V = L × W × H
- Total volume: Vtotal = V × N
- Waste allowance: Vwaste = Vtotal × (1 + w/100)
- Excavation allowance: Vexc = Vwaste × k
- Weight estimate: Weight = Vwaste × ρ
- Bag estimate: Bags = ceil(Vwaste ÷ yield)
D, L, W are cross-section dimensions, H is depth/height, N is pier count, w is waste percent, k is oversize multiplier, and ρ is concrete density.
How to use this calculator
- Select your unit system and pier shape.
- Enter pier size (diameter or length/width) and depth.
- Set the number of piers for the project.
- Add waste percent for spillage and uneven holes.
- Adjust the excavation multiplier if holes are oversized.
- Optionally add pricing to estimate concrete cost.
- Press Calculate to view results and download files.
Accurate pier inputs prevent overruns and delays onsite.