Concrete Calculator
Multi-purpose concrete volume calculator for slabs, footings, columns, and walls.
Formula & Explanation
This general-purpose calculator handles multiple concrete shapes: **Slab** (rectangular): Volume = Length × Width × (Thickness ÷ 12) **Footing** (rectangular): Volume = Length × Width × Depth **Column** (cylindrical): Volume = π × (Diameter ÷ 24)² × Height **Wall** (rectangular): Volume = Length × Height × (Thickness ÷ 12) After calculating the shape's volume, the calculator adds the waste percentage and divides by bag yield to determine bags needed. All volumes are then converted to cubic yards by dividing by 27.
Assumptions
- •Select the correct shape for your project
- •For slabs and walls, thickness is in inches; for columns, diameter is in inches
- •Length/width/height dimensions are in feet
- •Bag yield values (0.45 cu ft for 60 lb, 0.60 cu ft for 80 lb) are industry standards-confirm with your product
- •A 10% waste allowance is typical; adjust based on complexity and experience
Example Calculation
A 20 ft × 15 ft × 4" slab requires 100 cubic feet of concrete, or 248 bags with 10% waste allowance.
Inputs
Results
Quick Reference: Common Concrete Shapes
| shape | volume | bags_60lb |
|---|---|---|
| Slab 10×10×4" | 33.33 cu ft | 82 |
| Footing 4×4×2ft | 32 cu ft | 79 |
| Column 12"Ø×10ft | 7.85 cu ft | 20 |
| Wall 20×8×8" | 106.67 cu ft | 263 |
| Slab 20×15×6" | 150 cu ft | 372 |
Frequently Asked Questions
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