Concrete Footing Calculator
Concrete footings carry walls, columns, and building loads into the ground. Order too little and you risk a cold joint or short pour; order too much and you pay for unused yards. Volume comes from length × width × depth of the concrete prism. Add about 5–10% extra for trench irregularities, form gaps, and placement variation.
See also concrete calculator and post hole gravel calculator for backfill around posts.
Rectangular footing
Calculation is based on average density of 2400 kg/m³.
Calculation Results
Concrete volume
0.00 m³
Concrete weight
0.00 t
How much concrete do you need for footings?
Footings spread loads over soil or rock. The concrete quantity is the volume of the footing shape you will place—usually modeled as a box for estimating. This page is a quantity aid only; width, depth, and reinforcement must still follow your plans and local code.
How this calculator works
- Volume = length × width × depth
- Weight = volume × concrete density
Default density is 2400 kg/m³ for typical structural concrete. Inputs are converted to meters internally, so you can mix feet, inches, meters, and yards without manual conversion.
Understanding footing dimensions
Footings are often wider and deeper than the wall or post they support. Common planning ideas include:
- Width: often on the order of 2–3× wall thickness for spread footings (design governs).
- Depth: driven by load, soil bearing, and drainage; may need to reach competent soil.
- Placement: in cold climates, depth often must clear the frost line per code.
Small changes in width or depth move total volume quickly—always recheck if the engineer changes the section.
Where this calculator is used
It fits strip footings or rectangular pad segments such as:
- Building foundations
- Retaining wall bases
- Column and pier pads
- Fence post footings (when modeled as a box)
- Structural load-bearing bases
Split stepped or L-shaped runs into multiple rectangles and add the volumes for the full pour.
Example calculation
For a footing that is:
- 30 ft long
- 2 ft wide
- 1 ft deep
That is roughly 1.7 m³ of concrete and about 4.1 metric tons at 2400 kg/m³. Add extra for continuous pouring if your trench is rough or forms leak—do not rely on the net number alone.
Common mistakes to avoid
- Underestimating width. Footings spread load; a section that is too narrow fails bearing checks even if depth looks generous.
- Ignoring soil conditions. Soft or loose soils need wider, deeper, or engineered solutions beyond a generic volume guess.
- Stopping and starting pours without a plan. Structural footings are often specified as continuous lifts; know your jointing rules before you schedule trucks.
- Forgetting trench irregularities. Hand-dug or rocky trenches are not perfect prisms—extra volume is normal.
Practical tips for footing construction
- Level and compact trench bottoms where the design calls for it.
- Use formwork when side soils will not stand cleanly during the pour.
- Set reinforcement before the pour per lap and cover details.
- Avoid placing concrete into standing water or during conditions that violate the mix supplier’s limits.
Frequently asked questions
How deep should footings be?
Depth depends on soil type, loads, and climate. In colder regions, footings typically must sit below the local frost line. Use your jurisdiction’s code and any soils report you have—not guesswork from a generic sketch.
Do all structures require footings?
Anything that bears weight down to the ground needs a load path designed for the soil you have. Decorative features may be exempt; structural work is not.
Can I adjust footing size after calculation?
Yes—just re-enter dimensions here whenever length, width, or depth changes so your order matches the new section.
What happens if footings are too shallow?
You risk settlement, frost movement, and cracking. Repair usually means excavating and rebuilding—far more costly than sizing footings correctly up front.