Concrete Footing Calculator

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A proper concrete footing is the foundation of any structure — it spreads the building's weight across the soil below and prevents settling. Our Concrete Footing Calculator helps you determine exactly how much concrete you need for isolated footings (like for deck posts) or continuous strip footings (for foundation walls).

For isolated footings — the square or rectangular pads that sit under individual deck posts or column bases — simply enter the length, width, and depth. For continuous footings that run under an entire foundation wall, measure the total length of the wall, enter a typical width (usually 16–24 inches), and the required depth. The calculator handles multiple identical footings at once.

Several factors affect footing design: soil bearing capacity, local frost line depth, the weight of the structure being supported, and local building codes. In areas with expansive clay soils, footings may need to be deeper or wider to prevent movement during wet-dry cycles. Always have your footing design approved before pouring.

Remember that footings should be poured on undisturbed soil — never on fill dirt or previously dug areas unless properly compacted. Excavate the hole, verify the bottom is level, add any required reinforcement, then pour the concrete and level the top. For deck footings, the top of the footing should be at or slightly above ground level to prevent water accumulation around the post base.

Formula
Volume = Length × Width × (Depth ÷ 12) × Quantity

FAQ

How deep should a concrete footing be?
Footings should extend below the local frost line — typically 12–48 inches deep depending on your climate. Check with your local building department for the required frost line depth in your area.
What size footing do I need?
Footing size depends on the load it supports and bearing capacity of your soil. A typical residential deck footing is 24–36 inches square. Always verify size with your plans or structural engineer.
Do footings need reinforcement?
Footings for decks and light structures often don't require rebar, but it's recommended for added strength. Foundation walls and heavily loaded footings typically require #4 rebar both vertically and horizontally.
Can I pour footings in the rain?
Light rain is generally fine for freshly poured footings — the water helps with curing. However, heavy rain can wash out cement from the surface of unprotected concrete. Cover footings with plastic if heavy rain is expected within 24 hours of pouring.

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