Footing Calculator
Calculate concrete footing dimensions and materials for foundation walls, deck posts, and column piers. Includes rebar, volume, and load capacity estimates.
How to Use This Calculator
Calculate concrete footing requirements:
- Select footing type: continuous (walls), square (posts), or round (piers)
- Enter dimensions - length and width for continuous, size for pads
- Select depth based on your frost line requirements
- Specify quantity for multiple pad or pier footings
- Enter wall thickness for continuous footings to check sizing
Why This Matters
Properly sized footings are critical for structural integrity. Undersized footings can settle unevenly, causing cracks in walls, doors that stick, and even structural failure. Footings must bear on undisturbed soil below the frost line.
- Calculate concrete volume for any footing type
- Determine rebar requirements and placement
- Verify footing width meets load requirements
- Estimate load capacity based on soil bearing
Worked Examples
Continuous Foundation Footing
40 foot wall, 8 inch block, 16 inch wide, 8 inch deep
Calculation: 40 × (16/12) × (8/12) = 35.5 cu ft = 1.3 cu yards
Result: 1.3 cu yards concrete, 80 ft of #4 rebar
Deck Post Pad Footings
Four 24×24×12 inch pad footings
Calculation: 4 cu ft each × 4 = 16 cu ft = 0.59 cu yards
Result: 13 bags (80lb), 32 ft rebar in grid pattern
Common Mistakes to Avoid
- Not digging below frost line (causes heaving)
- Pouring on loose fill instead of undisturbed soil
- Making footings too narrow for the load
- Not providing 3 inch minimum concrete cover over rebar
- Forgetting vertical rebar dowels for wall tie-in