Concrete Footing Calculator
Estimate concrete for identical rectangular strip footings using length, width, depth and footing count. See cubic feet, cubic yards and an optional ordering allowance.
Estimate footing concrete
Measure the actual excavation or form dimensions. All footings in this calculation are assumed to be identical.
Rectangular footing • volume = length × width × depth × count
How to calculate concrete for footings
For rectangular footings, multiply the three dimensions to find the volume of one footing. Multiply by the number of identical footings, then convert cubic feet to cubic yards. The depth field uses inches, so divide that measurement by 12 first.
Use the actual formed or excavated length, in feet. Account for separate runs individually if they differ.
Use the concrete dimensions rather than the nominal wall or post size. Depth is entered in inches.
Divide cubic feet by 27 for cubic yards. Apply a separately chosen allowance only when appropriate.
Worked example: four strip footings
Four identical footings are each 12 ft long, 2 ft wide and 12 in deep. One footing requires 12 × 2 × (12 ÷ 12) = 24 ft³. Four footings require 96 ft³, or 3.56 yd³ before any allowance. With a 10% allowance, the planning estimate becomes 105.6 ft³ (3.91 yd³). These figures describe material volume, not a recommended footing design.
Concrete quantities for sample footings
These examples assume rectangular footings and exclude over-excavation and waste. They are arithmetic examples, not structural sizing guidance.
| Length | Width | Depth | Count | Volume (yd³) |
|---|---|---|---|---|
| 8 ft | 2 ft | 12 in | 1 | 0.59 |
| 12 ft | 2 ft | 12 in | 4 | 3.56 |
| 20 ft | 2 ft | 12 in | 2 | 2.96 |
| 30 ft | 2.5 ft | 12 in | 1 | 2.78 |
When to add an allowance
Extra concrete may be needed if excavation walls are irregular, forms vary, or spillage is expected. The calculator shows the base quantity separately from the allowance so you can choose a realistic figure rather than treating a fixed percentage as universal.
Different footing sizes?
Run a separate calculation for each distinct size, then add the resulting cubic yards. Do not use the footing count field for a mix of different lengths, widths or depths.
What this footing estimate does and does not cover
Included
Rectangular concrete volume, repeated identical footings, conversion between cubic feet and cubic yards, and an optional material allowance.
Not included
Stepped footings, sloped trenches, isolated pad footings with different geometry, rebar displacement, footing strength, soil bearing capacity, frost depth or required structural dimensions.
Important: footing sizing is a design decision
A material calculator cannot determine whether a footing is safe. Required dimensions depend on the building loads, soil, climate and local building requirements. Have footing design and reinforcement confirmed by the appropriate qualified professional or building authority.
Concrete footing calculator FAQs
How do I calculate concrete for several footings?
Find the volume of one rectangular footing and multiply it by the number of identical footings. Divide the total cubic feet by 27 to obtain cubic yards.
Does the result include concrete waste?
The base result does not. Enter an extra concrete allowance to see a separate adjusted quantity. Choose the allowance based on site conditions and supplier guidance.
Why is footing depth entered in inches?
Footing depth is commonly measured in inches. The calculator converts it to feet internally before multiplying the dimensions.
Can this tool determine the required footing size?
No. It calculates material quantity from dimensions you provide, not structural capacity or code compliance.
What if my footings have different dimensions?
Calculate each footing group separately, then add the concrete quantities. The count field assumes identical dimensions within each group.
Should I round the concrete order up?
Confirm the final order with your ready-mix supplier or bagged-concrete product yield. Suppliers may have ordering increments, minimum loads or other constraints.
Continue planning your project
CalcLounge provides preliminary estimating tools. Verify quantities, material specifications and project requirements before purchasing.
RESULTS — share, print and reset
The tool's own breakdown above is used; this panel adds only the share, print and reset controls.