Concrete Footing Calculator
A standard 20-foot strip footing (2 feet wide, 12 inches deep) requires 1.48 cubic yards of concrete — about 74 bags of 80-lb mix. Enter your footing dimensions below for volume, bag count, and material cost for any footing type.
Pro Tips
- →Footing size depends on soil bearing capacity and load
- →Typical footings are twice the wall width
- →Depth must be below frost line in cold climates
- →Include rebar reinforcement as per code
- →Consult building codes for sizing requirements
Includes 10% waste factor
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Cost Estimate
Estimated material costs for your project
Recommendation: Ready-Mix Concrete
For projects over 1 cubic yard, ready-mix is typically more economical and easier to work with.
528 bags × 80lb
11.73 cubic yards + delivery
288 sq ft × $3.00–$8.00/sq ft
Prices vary by location and time. Contact local suppliers for accurate quotes.
For general step-by-step instructions, read our complete When To Use Rebar and Permit Requirements.
What This Calculator Covers
Footings are the concrete elements that transfer structural loads from a building or structure into the soil. This calculator handles three common footing types: strip footings (continuous beneath walls), pad footings (isolated beneath columns or posts), and stepped footings (for sloped sites).
Enter length, width, and depth to get cubic yards, bag count, and ready-mix volume. Add a 10% waste buffer automatically — included in all output.
Typical Footing Dimensions and Concrete Volumes
| Footing Type | Typical Size | Concrete Needed |
|---|---|---|
| Residential strip (20 ft) | 20 × 2 ft × 12 in | 1.48 cu yd (74 bags) |
| Garage strip (60 ft perimeter) | 60 × 2 ft × 12 in | 4.44 cu yd |
| Deck post pad | 24 × 24 × 12 in each | 0.44 cu yd (20 bags) per pad |
| Column pad | 36 × 36 × 18 in | 1.25 cu yd per pad |
| Basement perimeter (100 ft) | 100 × 2 ft × 12 in | 7.4 cu yd |
Footing Depth: Frost Line Requirements
Footings must extend below the frost line — the depth at which soil freezes in winter. Frost heave shifts footings and cracks foundations if this requirement is missed.
| Climate Region | Typical Frost Depth | Minimum Footing Depth |
|---|---|---|
| Deep South (FL, Gulf Coast) | None | 12 inches |
| Mid-Atlantic, Pacific Northwest | 12–18 inches | 18–24 inches |
| Midwest, Northeast | 36–42 inches | 42–48 inches |
| Northern states (MN, MT, ND) | 48–60 inches | 54–66 inches |
Always check your local building department — frost depth requirements vary by county and soil type.
Rebar Requirements
Most residential footings require two #4 rebar bars running lengthwise in the lower third of the footing depth. For strip footings:
- Horizontal bars: Two #4 bars continuous, 3 inches from bottom
- Vertical ties: #3 bar at 4-foot intervals connecting to foundation wall above
- Corner reinforcement: L-shaped or overlapping bars at all corners (minimum 24-inch lap)
For detailed reinforcement guidance, see when to use rebar in concrete.
Bagged vs. Ready-Mix for Footings
Footings use more concrete per linear foot than most people expect. A 40-foot foundation perimeter with standard 16×12-inch footings needs roughly 5 cubic yards — that's 225 bags of 80-lb mix, which is impractical to hand-mix.
Rule of thumb: Use ready-mix for footings over 2 cubic yards. Use bagged mix for isolated pads, short piers, or deck footings under 1 yard.
For the full foundation pour, see the concrete foundation calculator.