This page explains the measurement or planning assumption behind the result. When you need the project quantity itself, use Concrete Footing Calculator.
Use concrete dimensions, not excavation dimensions
Excavations can be wider than the concrete due to formwork, soil conditions or working space. Quantity should describe the concrete actually placed.
Keep different footing sizes separate
A house or wall can use several footing dimensions. Calculate each size independently and add volumes rather than averaging cross-sections.
Separate structural design from volume
Soil bearing, reinforcement and footing width/depth are design issues. The quantity formula assumes those decisions have already been made.
Choose bulk or bagged supply after volume
Small footings may use premix; larger continuous runs often make ready-mix more practical. Compare the final cubic yards with supplier minimums and access.
Record each footing segment from the design
Continuous footings often change width or depth at porches, bearing walls, steps or transitions. Instead of using the largest cross-section for the whole project or averaging unlike sections, list each dimension group and its run length. Confirm whether the plan dimension is the concrete size or an excavation size. If grade changes, the concrete depth may not be uniform. Add grade beams, pads or thickened sections as separate shapes. This segmented takeoff is easier to audit and makes it clear which design dimension produced each cubic-foot or cubic-yard subtotal before the placement allowance is added.
Planning workflow
Read the plan
Record footing concrete dimensions.
Calculate each run
L × W × D.
Add allowance and choose supply
Check yards and premix yields.
Verify the project inputs
Recheck the key measurement, product specification or layout assumption that controls this calculation before converting the result into a purchase quantity.
Example: two footing sizes
If one wall uses a 16 × 8 in footing and another uses 20 × 10 in, calculate their volumes separately. Averaging the widths and depths can distort the true concrete quantity.
Reference table
| Planning point | Use / formula | Verify before relying on it |
|---|---|---|
| Cross-section | Width × depth | Use concrete dimensions. |
| Run volume | cross-section × length | Separate unlike runs. |
| Supply | yd³ or bag yield | Check supplier/product. |
Frequently asked questions
Can this guide tell me the required footing size?
No. It explains quantity calculations after the footing has been designed.
Should I include the wall stem in footing volume?
Only if it is poured as part of the same concrete shape; otherwise calculate separate volumes.
How much extra concrete should I add?
Use an allowance appropriate to placement conditions; there is no universal percentage.
Planning note: Product coverage, yield, package size, installation instructions and project requirements take priority over generic examples. Verify the exact product and project before purchasing.