Concrete Footing Calculator

How to Use This Calculator

1. 1Measure the total linear length of your footing in feet — for a perimeter footing, add up all sides.
2. 2Enter the footing width in feet — typical continuous footings are 12 to 24 inches (1 to 2 ft) wide.
3. 3Enter the footing depth in feet — common depths are 8 to 12 inches (0.67 to 1 ft) for shallow footings, deeper for frost line requirements.
4. 4Click Calculate to get cubic yards, bag counts, and waste-adjusted totals.

About This Material

Concrete footings are the structural base that transfers building loads to the soil. They sit below grade and support foundation walls, columns, and posts. There are two main types: continuous (strip) footings that run along the length of a wall, and spread (pad) footings that support individual columns or posts. Continuous footings for residential construction are typically 12 to 24 inches wide and 8 to 12 inches deep, with the width being at least twice the thickness of the wall they support. For a standard 8-inch concrete block wall, the footing should be at least 16 inches wide and 8 inches deep. Spread footings for deck posts and columns are usually 24x24 inches or larger, depending on the load. The bottom of the footing must extend below the local frost line to prevent frost heave — this ranges from 12 inches in the southern United States to 48 inches or more in northern states and Canada. Local building codes specify the exact frost depth for your area. Footings must bear on undisturbed or properly compacted soil with adequate bearing capacity, typically 1,500 to 2,000 PSF for residential construction. Reinforcement for continuous footings consists of two #4 rebar bars running horizontally near the bottom of the footing, with vertical dowels extending up into the foundation wall at 48-inch intervals. Spread footings use a grid of #4 rebar on 12-inch centers in both directions. Footing concrete is specified at 3,000 to 3,500 PSI and should have a 4 to 5-inch slump for workability in the trench. Ready-mix delivery is the standard method for footings. Costs run $125 to $175 per cubic yard. A typical 1,500 sq ft house perimeter (140 linear feet of 16-inch-wide by 8-inch-deep footing) requires approximately 3.5 cubic yards of concrete.

Installation Tips

• •Dig the trench to the exact width and depth specified in your plans — over-excavation wastes concrete and money.
• •Level the bottom of the trench with a hand tamper before pouring — an uneven footing base causes differential settling.
• •Place rebar on chairs or brick fragments to maintain 3 inches of concrete cover below the steel.
• •Install vertical rebar dowels every 4 feet to tie the footing to the foundation wall above.
• •Do not pour footings on frozen ground or in standing water — both conditions prevent proper curing and reduce strength.

Common Mistakes to Avoid

• ⚠Making footings too narrow — the footing width must be at least twice the wall thickness to properly spread the load to the soil.
• ⚠Not extending footings below the frost line — shallow footings in cold climates will heave and crack the foundation above.
• ⚠Over-excavating the trench and backfilling with loose soil — footings must bear on undisturbed or mechanically compacted earth.
• ⚠Omitting rebar in continuous footings — unreinforced footings crack at stress points and lose structural integrity.
• ⚠Pouring the foundation wall the same day as the footing — allow the footing to set for at least 24 hours before loading it with forms and wall concrete.

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