Concrete Foundation Calculator
Enter the foundation length, footing size and wall height and thickness. You get the footing and wall concrete as one order in cubic yards or cubic meters, the ready-mix to book, truckloads, bag counts and an estimated cost.
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Foundation concrete = length × (footing width × depth + wall height × thickness), plus 10% waste, ÷ 27 for yards. A 140 ft foundation with a 20 × 10 in footing and a 3 ft, 8 in stem wall is 7.20 + 10.37 = 17.57 yd³. With waste that is 19.33 yd³, so order 19.5 yd³ of ready-mix, about 2 truckloads.
How to use this foundation calculator
- Choose stem wall or basement wall. The fields are the same; only the default wall height changes.
- Enter the foundation length measured along the wall centerline. For a 40 × 30 ft house with 8 in walls that is about 140 ft.
- Enter the footing width and depth from your plans.
- Enter the wall height and thickness. Height runs from the top of the footing to the top of the wall.
- Read the order: footing and wall volumes, total with waste, ready-mix to book, trucks and cost.
How to calculate foundation concrete
wall (ft³) = length × height × thickness (ft)
yd³ = (footing + wall) × (1 + waste) ÷ 27
Convert inches to feet by dividing by 12: a 20 in footing is 1.667 ft wide and an 8 in wall is 0.667 ft thick.
| Footing size | Concrete per 100 linear ft |
|---|---|
| 16 × 8 in | 3.29 yd³ |
| 20 × 10 in | 5.14 yd³ |
| 24 × 12 in | 7.41 yd³ |
| Wall thickness | Per 100 lf per ft of height | 100 lf, 4 ft high | 100 lf, 8 ft high |
|---|---|---|---|
| 8 in | 2.47 yd³ | 9.88 yd³ | 19.75 yd³ |
| 10 in | 3.09 yd³ | 12.35 yd³ | 24.69 yd³ |
| 12 in | 3.70 yd³ | 14.81 yd³ | 29.63 yd³ |
Volumes before waste. Footing and wall sizes depend on loads, soil and frost depth, so take them from your plans or local code. The calculator does not size them.
Ordering tips for a foundation pour
- Two pours, two ordersFootings and walls are usually poured on different days. Use the footing and wall lines in the table to book each pour.
- Round upReady-mix is commonly ordered in ½ yd³ steps. Running short mid-pour costs far more than a little extra.
- Plan the trucksA full truck typically carries around 8–10 yd³. Ask your supplier about their load size, short-load fees and pump access.
- Waste10% covers trenches that are wider or deeper than planned and forms that bulge. Use more for earth-formed footings.
Worked example
- Footing 140 ft × 20 × 10 in
- 140 × 1.667 × 0.833 = 194.4 ft³ = 7.20 yd³
- Stem wall 140 ft × 3 ft × 8 in
- 140 × 3 × 0.667 = 280 ft³ = 10.37 yd³
- Total + 10% waste
- 17.57 × 1.10 = 19.33 yd³
- Ready-mix to order
- 19.5 yd³ ≈ $3,218 at $165 per yd³
- Trucks
- About 2 loads
Frequently asked questions
How do I calculate concrete for a foundation?
Footing L × W × D plus wall L × H × T, all in feet. Add about 10% waste and divide by 27 for cubic yards.
What length do I use for a rectangular foundation?
The perimeter along the wall centerline. The outside perimeter counts corners twice and slightly overestimates.
How many yards of concrete for a 40 x 30 foundation?
With a 140 ft centerline, a 20 × 10 in footing and a 3 ft, 8 in stem wall, about 17.6 yd³, or 19.5 yd³ to order with waste. With an 8 ft basement wall, about 38.5 yd³ to order.
Should I pour the footing and wall at the same time?
Usually not. Footings go first and walls later, often with a keyway or dowels. Order each pour from its own line in the results.
How big should a foundation footing be?
It depends on loads, stories and soil, so use your plans or local code tables. This calculator does not size footings.
Should I use bags or ready-mix for a foundation?
Ready-mix. One cubic yard takes 45 bags of 80 lb, so even a small foundation would need hundreds of bags.
What this calculator assumes
- A continuous footing and wall of constant size along the whole length. Add piers, pads and pilasters separately with the pier calculator.
- Ready-mix rounded up to the next ½ yd³ (or ½ m³). Truck count assumes about 10 yd³ per load.
- 80 lb bags yield about 0.6 ft³ and 60 lb bags about 0.45 ft³.
- Footing and wall dimensions, rebar and frost depth must follow your plans and local building code. Price is an editable estimate before tax, delivery and pump fees.