Concrete Footing Calculator
Cubic yards for a strip footing under a wall, deck beam or foundation. Enter the total run of footing, its width and its depth (thickness). Formed footings waste little — 5% is the default; use 10% for a trench poured against dirt.
Order 1.50 yd³ ready-mix — plants ticket in ¼-yd³ and most charge a short-load fee under ~5 yd³.
- Net volume (35.6 ft³)
- 1.32 yd³
- Waste 5%
- + 0.07 yd³
- Ready-mix ticket
- 1.50 yd³
- Approx. weight
- 5,333 lb
- 80 lb bags
- 63
- 60 lb bags
- 83
- 40 lb bags
- 125
- Materials + delivery$125–$180 / yd³ · Sep 2026
- $288 – $370
- Installed (with labor)typ. $671
- $495 – $923
Quantities follow the ticket. Links may earn us a commission at no cost to you; they never change a number.
What will this footing job cost?
See the installed price range for these quantities and get up to 3 quotes from local contractors. Free, no obligation.
How to calculate footing by hand
Cubic yards = Length (ft) × Width (in) ÷ 12 × Depth (in) ÷ 12 ÷ 27
Worked example
- Cross-section: 16 in ÷ 12 × 8 in ÷ 12 = 0.89 ft².
- Volume: 40 ft × 0.89 ft² = 35.6 ft³ = 1.32 yd³.
- Waste 5%: 35.6 × 1.05 = 37.3 ft³ = 1.38 yd³ → ready-mix ticket 1.5 yd³.
- Bags instead: 37.3 ÷ 0.60 = 63 × 80 lb bags — a truck is cheaper above 1 yd³.
- 16″ × 8″ footing
- 0.033 yd³ per linear ft · 30 ft per yd³
- 20″ × 10″ footing
- 0.051 yd³ per linear ft · 19 ft per yd³
- 24″ × 12″ footing
- 0.074 yd³ per linear ft · 13.5 ft per yd³
- 12″ × 6″ deck footing
- 0.019 yd³ per linear ft · 54 ft per yd³
Questions crews ask
How much concrete do I need for a footing?
Width × depth (both in feet) gives the cross-section; multiply by the total length for cubic feet and divide by 27. A 40 ft run of 16 × 8″ footing is 35.6 ft³ = 1.32 yd³; order 1.5 yards with 5% waste.
How wide and deep should a footing be?
For a single-storey house on average soil, 16″ wide × 8″ deep is typical; two storeys 20″ × 10″; three storeys or poor soil 24″ × 12″. The rule of thumb is twice the wall thickness wide and as deep as the wall is thick. Local code and frost depth govern — check both.
How many bags of concrete for a footing?
Divide cubic feet (with waste) by 0.60 for 80 lb bags. A 20 ft run of 12 × 6″ deck footing is 10 ft³ → 10.5 with waste → 18 × 80 lb bags. Above about a yard (45 bags), order ready-mix.
What psi concrete for footings?
3,000 psi is standard for residential footings; 3,500–4,000 psi in freeze–thaw climates or where code requires. Footings do not need air entrainment unless exposed.
Does a footing need rebar?
Most codes require two #4 bars run continuously in residential footings, with 3″ of cover. Add more, or step up to #5, for wider footings, soft soil or seismic zones. The calculator counts concrete only.