Deck Footing Calculator — Concrete Volume and Bags
Convert approved round shaft and base dimensions into concrete volume and packaged-mix quantities without using the result to size a structural footing.
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View all saved project estimatesWhat does the deck footing calculator calculate?
Calculate each approved round pier shaft and footing base as separate cylinders, add their volumes, multiply by footing count, then apply a placement allowance. This calculator converts the result to cubic yards and product-label bag yield. It estimates concrete quantity only; it does not determine diameter, depth, reinforcement, soil capacity, or frost protection.
Round deck pier shaft and footing-base volume
Diameters are divided by twenty-four to convert inches to radius in feet, while heights are divided by twelve. Each round shaft and wider base is calculated as a cylinder. Their nonoverlapping volumes are added, multiplied by the number of identical footings, and increased once for placement allowance before conversion to yards or bags.
How to measure for an accurate estimate
- Use approved footing and pier dimensions; do not choose diameter, base thickness, or excavation depth from a concrete-volume estimate.
- Measure shaft height above the wider base so the base thickness is not included in both cylindrical volumes.
- Group only identical footings, then calculate corner, interior, stair, landing, or high-load footing shapes separately when plans differ.
- Confirm whether drawings show round, square, belled, stepped, formed, or proprietary foundations and model each distinct geometry appropriately.
Concrete for six round deck footings
Six approved footings each use a 12-inch-diameter shaft 30 inches above an 18-inch-diameter, 6-inch-thick round base, with 10% placement allowance and 0.60 cubic foot of yield per bag.
The exact geometry contains about 17.08 cubic feet. With allowance it requires about 18.79 cubic feet, or 0.696 cubic yard, which rounds to 32 bags at the entered product yield.Before you purchase material
- Arrange utility locating, permits, required excavation or reinforcement inspections, and approved frost-depth verification before placing concrete.
- Use the exact bag’s listed yield, concrete specification, water amount, mixing method, temperature limits, placement time, consolidation, and curing instructions.
- Compare safe packaged-mix handling and mixer capacity with ready-mix minimums, access, chute or pump needs, crew size, and continuous-placement requirements.
- Coordinate approved anchors, post bases, reinforcement, forms, uplift details, clearances, drainage, and concrete cover before the pour begins.
Common questions
How much concrete is needed for a deck footing?
Volume depends on the approved footing shape and dimensions. For a round cylinder, multiply pi by radius squared by height, using feet throughout. Add any wider base as a separate nonoverlapping shape, multiply by footing count, add a realistic placement allowance, then divide by the exact product’s labeled bag yield.
Can this calculator size deck footings?
No. Footing diameter and thickness depend on tributary loads, beam and joist geometry, soil bearing, live or snow load, post arrangement, frost protection, concrete and reinforcement details, and adopted requirements. Obtain approved dimensions before entering them; the calculator converts those dimensions into purchase volume only.
How deep should deck footings be?
Depth is site- and jurisdiction-specific. It can depend on undisturbed soil, local frost depth, attachment to a frost-protected structure, slope, expansive or poor soil, groundwater, scour, and approved foundation systems. Verify the locally required bottom elevation and excavation details before digging, inspection, or ordering concrete.
Should I use bags or ready-mix concrete?
Compare total volume, bag handling, mixer capacity, water control, placement time, crew size, access, supplier minimums, short-load fees, chute reach, pump needs, and the requirement for a continuous placement. The approved concrete specification and safe workable placement method matter more than choosing solely from material price.
Sources and reference standards
- International Code Council — 2024 IRC Chapter 5 DecksOfficial code-publisher provisions for deck footings, posts, beams, joists, loads, frost protection, and connections; local adoption can differ.
- American Wood Council — DCA 6 Residential Wood Deck GuidePrescriptive deck guidance covering framing plans, spans, posts, footings, connections, limitations, and local approval boundaries.
- QUIKRETE — Concrete Mix 1101 Specification DataManufacturer specification listing approximate packaged-concrete yields; use the yield printed for the exact product purchased.
- 811 Before You DigOfficial U.S. one-call resource for arranging underground utility marking before excavation.
See every citation and the calculators that use it in the calculator source index.
Use this result in a complete project plan
Deck planning guide
A deck is one connected system, not a platform area followed by a shopping list. Height, attachment, loads, soil, footing locations, beams, joists, board direction, stairs, guards and finish all affect downstream quantities. This guide preserves those dependencies so calculator results support an approved design rather than quietly becoming the design.
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