Concrete footing calculator
Turn a continuous trench measurement into a concrete quantity.
Calculating example…
Estimates only · see assumptions below
Your material estimate
Example estimate— yd³
- Cubic feet
- —
- Cubic meters
- —
Shape assumption. One uniform rectangular strip. Total length must avoid double-counting corners and intersections. No wall, pier or pad is included.
Or use premix bags
Choose one row. Whole bags rounded up after waste.
| Bag size | Typical yield | Bags |
|---|---|---|
| 80 lb | 0.60 ft³ | — |
| 60 lb | 0.45 ft³ | — |
| 40 lb | 0.30 ft³ | — |
Typical values; use the yield on the bag label. These are concrete premix bags, not plain cement.
Volume × your $/yd³. Excludes tax, delivery, short-load fees, labor and equipment. Truck capacity and minimum orders vary.
Enter positive dimensions to see a material estimate.
Estimates only. Displayed volumes use 3 decimals; calculations and bag rounding use unrounded values. Confirm supplier increments before ordering. Not construction, commercial or tax advice.
How to calculate
- Measure the shape shown above. Use the unit labels beside each field.
- Choose a waste allowance from 0–30%. The example starts at 10%.
- Read the waste-adjusted volume or choose one bag size. Add a material price if you have a quote.
- Copy or print the estimate, then verify the mix yield and order increments with your supplier.
The formula
Volume (ft³) = total length (ft) × width (in) ÷ 12 × depth (in) ÷ 12. Cubic yards = ft³ ÷ 27.
Waste-adjusted volume = measured volume × (1 + waste percent ÷ 100). One cubic foot is 0.028316846592 cubic meters. Bag counts round up once; displayed volumes round to three decimals.
Worked example
40 ft × (16 ÷ 12) ft × (8 ÷ 12) ft = 35.555556 ft³ = 1.316872 yd³ before waste. With 10% waste: 1.448560 yd³ and 66 typical 80 lb bags.
Ready-mix material cost = waste-adjusted cubic yards × your price per cubic yard. A bag cost, when entered, is whole bags × price per bag. Neither cost includes delivery, tax, short-load fees, labor or equipment.
Geometry estimates material only. It does not select concrete strength, reinforcement, dimensions or a construction method.
Frequently asked questions
How do I measure a footing around corners?
Use a consistent length convention and count every part of the concrete once. Intersections and corners can overlap; subtract overlaps rather than counting both legs in full.
Is footing width in inches?
Yes in US mode. Width and depth use inches, while the total run uses feet. Metric mode shows centimeters and meters.
Does this include the foundation wall?
No. Calculate the wall separately with the wall calculator and avoid counting any shared volume twice.
What if the trench is uneven?
Use measurements that represent the actual excavated volume and consider a suitable allowance. The tool assumes constant width and depth; it cannot inspect a trench.
Can I use it for a rectangular pad?
Yes, if you enter the pad length, width and depth in the labeled units. For multiple pads, the multi-slab tool may be easier.
Does it tell me code-compliant footing dimensions?
No. Soil, loads, frost depth and local requirements determine the design. This is a material estimate only.