Concrete calculator
Concrete footing
Continuous footing volume, ready-mix quantity, and whole-bag equivalent.
Calculator result and formula
Ready-mix order: 1.25 yd³
Formula: Footing length × width × depth × quantity ÷ 27 × (1 + waste)
Formula ID: CONC-FOOT-001 · Version 1.0.0.
Inputs
- Footing length: Finished continuous footing length Default: 20.
- Footing width: Footing width before waste Default: 2.
- Footing depth: Concrete depth/thickness Default: 8.
- Number of footings: Count identical continuous footings Default: 1.
- Waste factor: Allowance for placement, irregular excavation, and spill Default: 10.
How this calculator works
Use finished continuous-footing dimensions to establish concrete volume, then apply a visible waste allowance before supplier purchase rounding.
- Measure the continuous footing length along its centerline.
- Enter the actual width and concrete depth required by the approved design.
- Use the rounded result as a starting point for a ready-mix supplier quote.
Worked example: Example: a 20 ft long footing, 2 ft wide and 8 in deep contains about 1.0 yd³ of concrete before a 10% allowance. The reviewed formula rounds the order to a quarter-yard purchase increment.
Assumptions and limitations
- Footing geometry is treated as a continuous rectangle.
- Ready-mix quantity is rounded to the next 0.25 yd³.
- Bag and truck-load values are planning equivalents; confirm product yield and supplier delivery capacity.
- Waste is applied before purchase rounding.
Common questions
- Does this determine footing size?
- No. Footing dimensions, reinforcement, soil bearing and local requirements must be set by the responsible professional.
- Why is waste added?
- Excavation variation, placement loss and supplier ordering increments can make a net-volume-only order too small.
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