Concrete calculator
Concrete Footing Calculator
Choose a continuous strip footing or isolated pad footings, enter the designed dimensions, and get adjusted cubic feet, ready-mix cubic yards, and whole concrete bags.
Planning estimate, not a contractor quote. Review the assumptions and replace presets with local prices when available.
Method
How this calculator works
Concrete footings are volume takeoffs. Continuous footings are treated as long rectangular prisms, while isolated pads are calculated individually and multiplied by quantity. The calculator does not choose footing dimensions; use values from the project design or local requirements.
Continuous volume = run length × footing width × footing thickness. Pad volume = pad length × pad width × pad thickness × quantity. Adjusted volume adds the selected allowance. Ready-mix rounds up to 0.25 yd³ and bags round up to whole packages.
Worked example
A realistic starting point
A 40 ft continuous footing that is 16 in wide and 8 in thick contains 35.56 ft³, or 1.32 yd³. With 10% allowance it requires 39.11 ft³, so plan on 1.50 yd³ of ready-mix or 66 nominal 80 lb bags.
What changes the answer
Factors worth checking
Use designed dimensions
Width, thickness, founding depth, and reinforcement depend on loads, soil, frost conditions, and local requirements. Do not size a footing from the material result.
Split different sections
Calculate strip runs, pads, steps, and thickened areas separately when their dimensions differ, then combine the adjusted volumes.
Allow for excavation variation
Earth-formed trenches can widen or lose material at the sides. Forms and careful measurements usually reduce quantity uncertainty.
Compare bags with delivery
A high bag count adds mixing and handling time. Compare ready-mix minimums, short-load fees, access, and placement time.
Common questions
Concrete footings FAQ
How do I calculate concrete for a continuous footing?
Multiply total run length by footing width and thickness after converting every dimension to feet. Divide cubic feet by 27 for cubic yards, then add an allowance appropriate to the forms and excavation.
Can I calculate several pad footings at once?
Yes. Choose isolated pads, enter one pad’s designed dimensions, and enter the number of identical pads. Calculate pads with different sizes as separate scenarios.
How deep should a footing be?
Founding depth is not a volume-calculator decision. Frost depth, soil bearing, loads, drainage, and local code all matter, so use approved project dimensions.
Why is ready-mix rounded to a quarter yard?
The quarter-yard figure is a planning increment, not a supplier rule. Ask the local producer about its ordering increments, minimum load, and short-load charges.
Evidence
Sources & review
- QUIKRETE — Footers for WallsManufacturer context and reminder to verify frost depth and local specifications.
- QUIKRETE Concrete Mix Data SheetNominal bag yields and intended footing uses.
- ACI Reinforced Concrete Design HandbookIndustry reference confirming footing design is separate from quantity takeoff.
Published by Calcstead. Report a correction.
Method and source links reviewed September 4, 2026. Price presets are editable planning inputs and should be replaced with current local information.