What the animation shows
The animation and the step-by-step video above use your numbers. Here is the same walkthrough written out for the default example.
What you enter
- Total footing length: 60 ft. Add up every run. At corners, count the overlap once.
- Footing width: 16 in.
- Footing depth (thickness): 8 in.
- Extra for waste and spillage: 10 %. Typical allowance is 5–10%. Use more for uneven subgrade.
- Bag size: 80 lb bag. Yields used: 40 lb ≈ 0.30 ft³, 50 lb ≈ 0.375 ft³, 60 lb ≈ 0.45 ft³, 80 lb ≈ 0.60 ft³.
What happens, step by step
- Concrete runs along all 60 ft of trench as it is poured.
- The side view shows the 16 in × 8 in cross-section filling up.
- A long run is drawn folded into a rectangle of the same length.
- Length × width × depth, plus 10%, gives 2.17 cu yd.
The answer: concrete to order (with waste) is 2.17 cu yd.
How it’s calculated
- Volume = total length × width × depth
- Order = volume × (1 + waste %)
Worked example
60 ft of footing, 16 in wide by 8 in deep, 10% waste.
Inputs
- Total footing length
- 60 ft
- Footing width
- 16 in
- Footing depth (thickness)
- 8 in
- Extra for waste and spillage
- 10 %
- Bag size
- 80 lb bag
- Ready-mix price per cubic yard
- 0 $/yd³
Results
- Concrete to order (with waste)
- 2.17 cu yd
- Net volume
- 1.98 cu yd
- Or bags
- 98 bags
Assumptions and limits
- Rectangular cross-section along the whole run.
- Required footing width, depth and frost depth are set by your local code and soil — this tool only computes volume.
- Bag counts use typical manufacturer yields for pre-mixed concrete. Check the yield printed on your bag.
Verify the result against the applicable local code, adopted code edition, manufacturer instructions and project requirements. See our methodology.
Questions
How do I measure footing length at corners?
Measure along the centerline of the footing, or take outside lengths on two sides and inside lengths on the other two, so corners are not counted twice.
Can I use this for a concrete curb?
Yes. A straight curb is a rectangular cross-section along a length, the same as a strip footing.