How Much Concrete for 100 Feet of Footing?
For 100 linear feet of a 16 by 8 inch footing, plan on about 3.29 cubic yards. How much concrete for 100 feet of footing at other sizes is in the table; trench footings poured against the soil often use more than the math because trench walls are never perfectly straight.
Concrete calculator →Footing math
- Cross-section: 16 in × 8 in = 1.333 ft × 0.667 ft = 0.889 sq ft.
- Volume: 0.889 × 100 ft = 88.9 cu ft.
- Yards: ÷ 27 = 3.29 yd³.
Related: How Much Concrete for 20 Feet of Footing?
Yards for common footing sizes over 100 feet
| Footing (width × depth) | Cubic feet | Cubic yards | Yards +10% |
|---|---|---|---|
| 12 × 6 in | 50.0 | 1.85 | 2.04 |
| 16 × 8 in | 88.9 | 3.29 | 3.62 |
| 20 × 8 in | 111.1 | 4.12 | 4.53 |
| 24 × 10 in | 166.7 | 6.17 | 6.79 |
| 24 × 12 in | 200.0 | 7.41 | 8.15 |
How big the footing should be
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 16 Feet of Footing?
Trench pours run over
Earth-formed trenches eat extra concrete. Over-digging by an inch on each side of a 16-inch footing adds about 12 percent. Measure the trench after digging and size the order from those numbers.
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 100 feet of 16x8 footing?
About 3.29 cubic yards before waste.
How many yards for 100 feet of 24x12 footing?
About 7.41 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 60 Feet of Footing?
- How Much Concrete for 80 Feet of Footing?
As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.