Concrete Footing Calculator
Estimate a continuous strip footing with one total length and uniform cross-section. Use approved dimensions for any structural or permitted foundation.
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View all saved project estimatesWhat does the concrete footing calculator calculate?
Multiply the footing’s total centerline length by its width and depth, converting inches to feet, then divide by 27 for cubic yards. Add a placement allowance for trench variation. This tool estimates volume only; footing size, reinforcement, frost depth, and bearing require professional or code verification.
Continuous rectangular footing volume
Width and depth form the footing cross-section in square feet. Multiplying by total length gives cubic feet; the calculator converts this to yards and adds the chosen trench allowance.
How to measure for an accurate estimate
- Use approved footing width and depth rather than the visible trench alone.
- Measure total length using a consistent centerline or segment method so corners are counted once.
- Calculate stepped footings and sections with different cross-sections separately.
- Measure over-excavation before the pour because soil collapse can materially increase concrete volume.
Continuous perimeter footing
An 80 ft footing is 16 inches wide and 8 inches deep, with 10% trench allowance.
80 × (16 ÷ 12) × (8 ÷ 12) ÷ 27 = 2.63 cu yd; order estimate = 2.90 cu yd.Before you purchase material
- Arrange required footing inspection before ordering concrete or covering reinforcement.
- Confirm mix specification, placement access, pump needs, and allowable construction joints.
- Have forms, reinforcement, chairs, anchor items, tools, crew, and washout ready before delivery.
- Budget delivery and short-load fees separately from the displayed material subtotal.
Common questions
How do I measure the length of a continuous footing?
Use the plan’s centerline dimensions when available. Otherwise divide the footprint into non-overlapping straight segments and document how corners are handled. Mixing inside, outside, and centerline lengths can double-count or omit concrete at intersections.
How much extra concrete should I allow for footings?
Formed footings may need less extra than earth-formed trenches. Ten percent is a planning starting point when soil variation exists, but actual allowance depends on excavation control, collapse, pumping, and supplier increments. Measure the trench before ordering.
Can this calculator determine footing width or depth?
No. It calculates concrete from dimensions you already have. Required width and depth depend on loads, soil bearing, frost conditions, seismic or wind design, and code. Obtain approved dimensions from a qualified professional or local building authority.
Do I include rebar volume when ordering footing concrete?
Concrete estimators normally do not deduct reinforcement displacement because the difference is small relative to placement variation. Order from the full geometric volume and calculate reinforcing steel separately from approved plans, including laps, bends, and supports.
Sources and reference standards
- International Code Council — 2024 International Residential CodePrimary model-code source for residential foundations, reinforcement, masonry, and stair safety requirements.
- Concrete Reinforcing Steel InstituteIndustry source explaining reinforced-concrete materials and placement fundamentals.
See every citation and the calculators that use it in the calculator source index.
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