Calculate cubic yards, bags, and cost for continuous footings, spread footings, and pier footings
Footings are the base of any structure — they transfer loads from walls, columns, and beams into the soil below. Getting footing dimensions right is critical for structural integrity and code compliance.
Footings must extend below the local frost depth to prevent frost heave. Typical frost depths by region:
| Application | Width | Depth | Concrete per Linear Foot |
|---|---|---|---|
| Interior wall footing | 12 in | 12 in | 0.037 yd3 |
| Exterior wall footing | 18 in | 12 in | 0.056 yd3 |
| Load-bearing wall | 24 in | 12 in | 0.074 yd3 |
| Deck pier (12" dia, 3 ft deep) | 12 in dia | 36 in | 0.11 yd3 each |
| Deck pier (16" dia, 4 ft deep) | 16 in dia | 48 in | 0.26 yd3 each |
Most residential footings require a minimum of two #4 rebar bars running horizontally the full length of continuous footings. Pier footings typically use a cage of 4-6 vertical bars with horizontal ties. Always follow your local building department's requirements — footing rebar is inspected before pouring in most jurisdictions.
Footing depth depends primarily on the local frost line. In warm climates (FL, TX) footings may only need to be 12 inches deep. In northern states (MN, WI) footings must extend 48-72 inches below grade. Always check your local building code for the minimum footing depth requirement.
A standard rule of thumb is to make the footing twice as wide as the wall it supports. For an 8-inch wall, use a 16-inch footing. For a 12-inch wall, use a 24-inch footing. Spread footings for columns are typically 2-3 feet wide. Always follow your engineer's or building department's specifications.
Multiply footing length x width x depth (all in feet) to get cubic feet, then divide by 27 for cubic yards. Add 10% for waste. Use our calculator above for instant results. For a 40-linear-foot perimeter with 18-inch wide, 12-inch deep footings, you need approximately 2.22 cubic yards.
Yes — virtually all structural footings require rebar. Continuous footings typically need two #4 horizontal bars. Spread footings and pier footings need a rebar cage. Even simple deck footings benefit from a single vertical #4 bar to tie into the post anchor. Rebar inspection is required before pouring in most jurisdictions.