Concrete Footing Calculator

A concrete footing calculator helps you estimate how much concrete a strip footing, trench footing, or foundation base needs before the pour begins. Contractors, builders, engineers, and DIY users rely on a concrete footing calculator when they want a quick volume estimate for footing runs under walls, sheds, decks, garages, or small extensions.

The result matters because footing concrete is usually ordered before reinforcement, labour, and inspection schedules are locked in. A shallow underestimate can delay the pour, while a large overestimate increases cost and waste.

How to Use the Concrete Footing Calculator

1. Enter the footing length, width, and depth using one consistent unit system.
2. Add the number of footing runs if the project has more than one identical section.
3. Include a waste allowance if the trench is irregular, over-dug, or likely to lose volume into loose soil.
4. Review the total concrete volume in cubic feet, cubic metres, or cubic yards depending on the calculator output.
5. Convert the result into bags or ready-mix order quantity if that helps with purchasing.

If the footing steps up or down along a slope, estimate each section separately. A single average depth can hide a meaningful volume difference.

What the Concrete Footing Calculator Measures

The calculator measures the concrete volume required to fill the footing dimensions provided.

Input	What it means	Example
Footing length	Total run of the footing	40 ft
Footing width	Width across the trench	16 in
Footing depth	Thickness or fill depth	12 in
Output	Concrete volume	53.3 cu ft or 1.98 cu yd

That makes the tool useful for ready-mix ordering, comparing bagged-concrete alternatives, and checking excavation quantities before the pour.

Concrete Footing Formula

The basic formula is:

Footing volume = Length x Width x Depth x Number of runs
Cubic yards = Cubic feet / 27
Adjusted volume = Footing volume x (1 + Waste percentage)

When width or depth is measured in inches, convert those values to feet before multiplying if the calculator is working in cubic feet.

Example Concrete Footing Calculation

Suppose a footing has these dimensions:

• Length: 40 ft
• Width: 16 in or 1.333 ft
• Depth: 12 in or 1 ft
• Number of runs: 1
• Waste allowance: 10%

The calculation is:

Base volume = 40 x 1.333 x 1 = 53.3 cu ft
Cubic yards = 53.3 / 27 = 1.98 cu yd
Adjusted volume = 1.98 x 1.10 = 2.18 cu yd

That means the footing would usually be ordered at about 2.18 cubic yards after including a modest waste allowance for real site conditions.

What Changes Footing Volume Most

Width and depth changes

Small increases in footing thickness or width can add a surprising amount of concrete over a long run.

Stepped or sloped footings

Projects on uneven ground often need several separate estimates because each step can change the total volume.

Over-excavation

Loose soil, trench collapse, or machine overdig can raise the actual fill volume beyond the design dimensions.

Bell ends or thickened sections

Some footings have enlarged ends, piers, or pads that should be estimated separately from the main run.

Common Concrete Footing Mistakes

• Forgetting to convert inches to feet before calculating volume.
• Using one average depth for a stepped footing.
• Ignoring over-excavation in loose or wet ground.
• Ordering from design dimensions only when the actual trench is wider.
• Treating footing volume as the same as slab volume without checking the geometry.

If you want to connect the volume with ordering decisions, compare this page with a Concrete Bag Calculator, Concrete Slab Calculator, Cement Calculator, or Excavation Calculator.

FAQ

How do I calculate footing concrete volume?

Multiply the footing length by width and depth, then apply the number of runs and any waste allowance if needed.

Why do I need a waste allowance for footings?

Real trenches are not always exact. Overdig, uneven sides, and loose soil can all increase the amount of concrete required.

Should footing width and depth be measured in inches or feet?

Either is fine, but the units must be consistent. If you are calculating cubic feet, convert inches to feet before multiplying.

Can this calculator help me decide between bags and ready-mix?

Yes. Once you know the total footing volume, you can compare it against the yield of bagged concrete or the minimum order for ready-mix.

What if the footing has steps or thickened sections?

Estimate each section separately and add the volumes together. That approach is more reliable than using one average dimension.