Concrete Footing Calculator
Calculate concrete volume for continuous footings, pier (sonotube) footings, and spread footings. Get cubic feet, cubic yards, and bag counts.
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Cubic Yards
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Cubic Feet —
80 lb Bags —
60 lb Bags —
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Cubic Yards
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80 lb Bags —
Cubic Feet —
Professional Full parameters & maximum detail ▾
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Concrete
Cubic Yards —
80 lb Bags —
Reinforcement & Hardware
Rebar Linear Feet —
Footing Below Frost —
Cost
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How to Use This Calculator
- Select footing type (rectangular or cylindrical).
- Enter width/diameter, depth, and length or count.
- Results show cubic feet, cubic yards, and bag counts.
Formula
Rectangular: L × W × D
Cylindrical (pier): π × r² × Depth × Count
Cubic yards = Cu ft ÷ 27 | 80 lb bags ≈ cu yd × 45
Example
Example: 40 ft continuous footing, 16 in wide, 12 in deep → 53.3 cu ft → 1.97 yd³ → 89 bags of 80 lb.
Frequently Asked Questions
- For a continuous footing: Length × Width × Depth. For a pier: π × r² × Depth. Divide by 27 for cubic yards. Add 10% waste.
- Footings must extend below the local frost depth. In cold climates that may be 36–48 inches. Check your local building code.
- A sonotube (cardboard form tube) creates a cylindrical pier footing. Common sizes are 8", 10", 12", and 16" diameter.
- Use π × r² × depth for one tube, multiply by count, divide by 27 for cubic yards. A 12" tube at 4 ft deep = 0.175 yd³ each, so 10 = 1.75 yd³.
- A general rule is the footing width should be twice the wall thickness. A structural engineer should size footings for load-bearing applications.