Concrete footing calculator
Work out the concrete volume for a continuous strip footing under a wall or fence line.
Concrete footing calculator
Work out the concrete volume for a continuous strip footing under a wall or fence line.
Enter your footing dimensions to see the concrete estimate.
Concrete needed
Project summary
How it works
These are volume estimates for planning. Actual concrete requirements depend on form dimensions, subgrade and waste.
Concrete footing calculator
Long and narrow, not length times width
A footing is a different shape question from a slab: it runs the length of a wall or fence line but is only as wide and deep as the cross-section calls for, often measured in inches rather than feet. This calculator keeps width and depth in inches specifically because footing cross-sections are usually small numbers that get lost if you have to convert them yourself.
Rebar is a quantity, not a design
The optional rebar figure here is simple linear footage: the number of horizontal bar runs you plan to place, multiplied by the footing length. It tells you how much bar to buy, not how much a footing actually needs structurally. Bar size, spacing and placement depend on the load the footing carries and on local code, so check those before you dig.
Frequently asked questions
How much concrete does a 20 foot footing need?
A 20 foot footing that is 8 inches wide and 12 inches deep needs about 13.3 cubic feet of concrete, or roughly 0.49 cubic yards. With a 10 percent waste allowance that is closer to 0.54 cubic yards. Enter your own footing dimensions above for the exact figure.
How deep should a footing be?
Footing depth is set primarily by the local frost line, so it varies significantly by region and is set by local building code, not by a single rule of thumb. Check with your local building department for the required footing depth before digging.
How many bags of concrete per footing?
A typical 12 inch diameter footing that is 3 feet deep takes about three 60 pound bags of concrete mix. Larger footings or deeper holes take more. The calculator shows total cubic feet and bags based on your footing dimensions.
How deep should concrete footings be?
Footings must extend below the frost line, which ranges from 12 inches in warm climates to 48 inches or more in cold regions. Check your local building code for the frost line depth. The calculator counts footings and volume, and you set the depth to match your code.
What size footings do I need?
Most residential footings are 12 to 24 inches in diameter. The size depends on the load and soil conditions. Your structural engineer or local building code specifies the required size. The calculator lets you enter diameter and depth to get the volume.
Do I need a footing for every post?
Yes, each post should rest on its own footing to transfer the load to the soil. The calculator counts footings based on your structure layout, and each footing supports one post or column.
How much does a concrete footing cost?
Cost depends on size and depth. A typical residential footing costs 50 to 150 dollars each including concrete and labour. The calculator gives you the total volume so you can estimate material costs for all footings combined.
Can I use tube forms for footings?
Cardboard tube forms, commonly called sono tubes, are the standard method for forming round footings. They keep the concrete contained while it cures and can be left in the ground. The calculator shows the volume needed to fill the tubes you select.