Concrete quantity guide
How to calculate concrete for a footing and stem wall
Calculate the footing and stem wall as two separate, non-overlapping rectangular volumes. Add their net volumes only after each component has been checked.
Calculate the footing01 / Read the section
Treat the footing and stem wall as separate parts
The footing is the wider base. The stem wall is the narrower wall above it. A foundation detail can use another arrangement, so use the dimensions and relationships shown in the project documents.
A HUD guide to residential concrete masonry explains that a foundation may combine a footing, wall, slab, pile, or pier and illustrates stem-wall and monolithic slab systems separately. This article uses that component distinction only for quantity arithmetic and does not interpret design requirements.
02 / Collect the dimensions
Use one run and two cross-sections
- 1
Total run length
Measure the continuous footing run using the method required by the drawings or takeoff. Divide changing widths or depths into separate sections.
- 2
Footing width and depth
Use the finished footing dimensions. These form the lower rectangular prism.
- 3
Stem-wall thickness and height
For this method, measure wall height upward from the top of the footing. Do not include the footing depth again.
A historic HUD stem-wall foundation study documents configurations without a separate spread footing. That is one reason to match the calculation to the actual detail instead of assuming every foundation has the section shown above.
03 / Calculate each volume
Keep the component quantities visible
| Quantity | Formula | Purpose |
|---|---|---|
| Footing net volume | run × footing width × footing depth | Lower base only |
| Stem-wall net volume | run × wall thickness × wall height | Wall above the footing only |
| Combined net volume | footing volume + wall volume | Geometric concrete quantity |
| Allowance volume | combined net volume × chosen percentage | Separate procurement choice |
| Estimated order | combined net volume + allowance volume | Quantity before supplier rounding |
Use consistent units before multiplying. The net quantities should remain visible even if footing and wall concrete will be ordered together.
04 / Worked example
A 12 m footing and stem wall
Assume the project detail gives a 12 m run, a 0.60 m × 0.25 m footing, and a 0.20 m thick stem wall that rises 0.80 m above the footing.
| Footing | 12 × 0.60 × 0.25 | 1.80 m³ |
|---|---|---|
| Stem wall | 12 × 0.20 × 0.80 | 1.92 m³ |
| Combined net volume | 1.80 + 1.92 | 3.72 m³ |
| Illustrative 5% allowance | 3.72 × 0.05 | 0.186 m³ |
| Illustrative order quantity | 3.72 + 0.186 | 3.906 m³ |
The 5% allowance is an example, not a recommendation. Using the approximate building conversion in this NIST unit reference, the 3.72 m³ net quantity is approximately 4.8658 yd³.
05 / Check the boundary
Do not count the shared section twice
The worked method assumes the wall height starts at the top of the footing. If a drawing gives a total height from the bottom of the footing to the top of the wall, using that full height in the wall calculation would count part of the footing twice.
Some systems are monolithic, stepped, thickened, keyed, or shaped differently. Break irregular geometry into non-overlapping parts or use a project-specific takeoff. This guide does not determine structural dimensions or construction details.
06 / Use both calculators
Transfer the net quantities, not assumed dimensions
1. Calculate the footing
Use the Concrete Footing Calculator for the known continuous run, width, and depth. Record its net footing volume before allowance.
2. Calculate the stem wall
Use the Poured Concrete Wall Calculator for the known wall run, height above the footing, and thickness. Record its net wall volume.
3. Reconcile the total
Add the two net quantities. Keep allowance, supplier rounding, bags, rates, and cost separate so the underlying geometry can still be checked.
Next step
Start with the footing shown on your drawings.
Calculate its net volume, then use the wall calculator for the separate stem-wall quantity.