How Much Concrete for 40 Feet of Footing?
How much concrete for 40 feet of footing depends on the footing’s width and depth. A common residential footing 16 inches wide by 8 inches deep works out to about 1.32 cubic yards over 40 feet, before waste.
Concrete calculator →Footing math
- Cross-section: 16 in × 8 in = 1.333 ft × 0.667 ft = 0.889 sq ft.
- Volume: 0.889 × 40 ft = 35.6 cu ft.
- Yards: ÷ 27 = 1.32 yd³.
Related: How Much Concrete for 100 Feet of Footing?
Yards for common footing sizes over 40 feet
| Footing (width × depth) | Cubic feet | Cubic yards | Yards +10% |
|---|---|---|---|
| 12 × 6 in | 20.0 | 0.74 | 0.81 |
| 16 × 8 in | 35.6 | 1.32 | 1.45 |
| 20 × 8 in | 44.4 | 1.65 | 1.81 |
| 24 × 10 in | 66.7 | 2.47 | 2.72 |
| 24 × 12 in | 80.0 | 2.96 | 3.26 |
Sizing and depth
Footing size comes from the load, the soil and local code. A frequently used rule of thumb is a footing about twice as wide as the wall it supports and at least as deep as the wall is thick, but your building department sets the real minimum. The bottom must sit below the local frost line. See footing depth and the frost line.
Related: How Much Concrete for 20 Feet of Footing?
Trench pours run over
When the footing is poured straight into a dug trench instead of forms, the sides wander and the bottom is rarely flat. Measure the actual trench at several points and add 10 to 15 percent, not the usual 5.
Rebar and inspection
Most footings carry horizontal rebar set on chairs or dobies so it sits a few inches above the soil. Many jurisdictions require an inspection of the trench and steel before the pour, so schedule it before you book the truck.
Questions people ask
How many yards for 40 feet of 16x8 footing?
About 1.32 cubic yards before waste.
How many yards for 40 feet of 24x12 footing?
About 2.96 cubic yards.
How much extra should I order for a trench footing?
About 10 to 15 percent, since trench walls are rarely straight.
How deep should a footing be?
Below the local frost line and on undisturbed soil; your building department sets the minimum.
How many 80 lb bags make a cubic yard?
About 45. Each 80 lb bag yields roughly 0.6 cubic feet, and a cubic yard is 27 cubic feet.
Related guides
- How Much Concrete for a Retaining Wall Footing?
- Footing Depth and the Frost Line: How Deep to Dig
- How Much Concrete for a Deck Footing? Bags per Hole
- How Much Area Does a Yard of Concrete Cover?
- How Many Bags of Concrete in a Yard? 40, 60, 80 lb
- Gravel Base Under a Concrete Slab: Depth and Tons
- How Many Yards in a Concrete Truck? Mixer Sizes
- Concrete Short Load Fee: What It Is and How to Cut It
- 60 lb vs 80 lb Concrete Bags: Yield, Count, and Cost
- Rebar vs Wire Mesh in a Slab: Which One to Use
- How Much Concrete for 24 Feet of Footing?
- How Much Concrete for 30 Feet of Footing?
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