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Calculate concrete volume for footings instantly. Get accurate measurements for continuous wall footings, square piers, and round piers with concrete bag estimates and optional rebar calculations.
Where V = volume in cubic yards, all dimensions in formula shown
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A concrete footing is a structural foundation element that distributes the weight of a building, wall, column, or deck to the soil beneath. Footings prevent settling and provide stability by spreading loads over a larger area.
There are three main types of concrete footings:
Example: 20 ft long, 2 ft wide, 12 in deep
V = (20 × 2 × 1) / 27
V = 1.48 cu yd
Example: 16 in × 16 in, 24 in deep
V = ((16/12)² × 2) / 27
V = 0.099 cu yd
Example: 12 in diameter, 36 in deep
V = (π × 0.5² × 3) / 27
V = 0.087 cu yd
Footings must extend below the frost line to prevent heaving. Check local building codes for exact requirements.
| Region | Typical Frost Depth | Minimum Footing Depth |
|---|---|---|
| Southern States (FL, TX, CA) | 6-12 inches | 12 inches |
| Mid-Atlantic (VA, NC, TN) | 24-36 inches | 36 inches |
| Northern States (NY, MI, WI) | 42-60 inches | 48-60 inches |
| Alaska | 60-100+ inches | 60-100 inches |
Note: Always verify with local building codes. Frost depths vary significantly within regions.
| Application | Recommended Width | Recommended Depth | Notes |
|---|---|---|---|
| Residential Wall (1-story) | 16 inches | 8 inches | Below frost line |
| Residential Wall (2-story) | 20-24 inches | 10-12 inches | Below frost line |
| Deck Post (small deck) | 16 x 16 inches | 12 inches | Below frost line |
| Deck Post (large deck) | 24 x 24 inches | 18 inches | Below frost line |
| Fence Post | 8-12 inches dia | 24-36 inches | Below frost line |
| Column/Beam Support | 24 x 24 inches | 12-18 inches | Engineer required |
Important: These are general guidelines. Actual footing sizes depend on soil bearing capacity, loads, and local codes. Consult a structural engineer for critical applications.
Footings must extend below the frost line for your region (typically 12-60 inches depending on climate). Minimum depth is usually 12 inches below grade. Always check local building codes for specific requirements.
The frost line is the maximum depth soil freezes in winter. If footings are above the frost line, freezing soil can expand and heave the structure upward, causing severe damage. Footings must always be placed below this depth.
Width depends on the load and soil bearing capacity. General rule: footings should be twice as wide as the wall they support. For a 6-inch wall, use a 12-16 inch wide footing. Heavier loads or poor soil require wider footings.
Most building codes require rebar in footings. Continuous footings typically use two horizontal #4 rebar bars running the length. Pier footings often use four vertical #4 bars. Rebar prevents cracking and increases structural strength.
An 80lb bag of concrete yields approximately 0.60 cubic feet (0.022 cubic yards). You'll need about 45 bags per cubic yard. A 60lb bag yields about 0.45 cubic feet, requiring 60 bags per cubic yard.
Yes, most jurisdictions require inspection before pouring concrete. The inspector verifies proper depth, width, rebar placement, and soil conditions. Never pour concrete before inspection approval or you may need to remove it.
Continuous footings are long strips that support walls, distributing the load along their length. Pier footings are isolated pads under posts or columns, supporting concentrated loads at specific points.
Concrete should not be poured when temperatures are below 40°F or expected to drop below freezing within 24 hours. Cold weather can prevent proper curing and weaken the concrete. Use heated enclosures or cold-weather concrete mixes if necessary.
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