Concrete Footing Calculator
Concrete footings transfer structural loads from a building to the soil below. This calculator handles two types: continuous strip footings (running the full perimeter of a wall) and isolated pad footings (individual pads under posts or columns). Enter footing dimensions, depth, and quantity to get total cubic yards, 60lb and 80lb bag counts, rebar requirements, and a material cost estimate. Footings must extend below the frost line — the depth at which ground freezes in your climate — to prevent seasonal heaving. In northern states this means 36–48 inches; in the South, 12–18 inches is often sufficient. Footing width should be at least twice the wall thickness above it, and minimum depth is 6 inches per IBC requirements. The calculator includes an estimated rebar quantity based on two longitudinal bars plus stirrups every 2 feet, which is standard for residential strip footings.
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How to Use This Calculator
- 1Enter your measurements in the fields above. Use the units shown next to each field (ft, in, etc.).
- 2Click Calculate to get your material estimate instantly.
- 3Review the highlighted result — it shows the key quantity you need to order.
- 4Use Copy Results to save your estimate, or bookmark the URL — your inputs are encoded in the link.
Pro tip: Always add 10% to your material order to account for waste, cuts, and defects.
Frequently Asked Questions
How deep should a concrete footing be?
Footings must extend below the frost line in your area to prevent heaving. In the northern US, frost depth is 36–48 inches. In the South, 12–18 inches is often acceptable. Check your local building code for the required depth.
What is the minimum width for a concrete footing?
The minimum footing width is typically twice the wall thickness above it. For an 8-inch concrete block wall, use a 16-inch-wide footing. Footings also must be as deep as they are wide (minimum) and at least 6 inches deep.
Do I need rebar in a concrete footing?
Yes, for structural footings. Concrete is strong in compression but weak in tension — rebar handles the tensile stress. Use at least two #4 (1/2") horizontal bars running the full length of strip footings, tied together with vertical stirrups every 24 inches. For isolated pad footings, use a grid of #4 bars at 12-inch spacing.
How much does a concrete footing cost?
Ready-mix concrete costs $125–$150 per cubic yard. A typical 40-foot perimeter footing (12" wide × 12" deep) requires about 1.5 cubic yards — roughly $200–$225 in concrete alone. Add rebar, forming lumber, and labor for the complete cost. DIY excavation and forming significantly reduces total project cost.