Footing concrete calculator
What you need
0.66 cu yd
- Cubic feet
- 17.78 cu ft
- Cubic metres
- 0.503 m³
- Order this much
- 0.72 cu yd
- 80 lb bags
- 33
- 60 lb bags
- 44
- Weight
- 2,490 lb
- Truckloads
- 1
- Cost
- $110 to $150
Common sizes
| Size | Cubic yards | 80 lb bags |
|---|---|---|
| 16″ × 8″ × 20′ | 0.66 | 33 |
| 16″ × 8″ × 40′ | 1.32 | 66 |
| 20″ × 10″ × 30′ | 1.54 | 77 |
| 24″ × 12″ × 20′ | 1.48 | 74 |
| 24″ × 12″ × 40′ | 2.96 | 147 |
| 12″ × 6″ × 20′ | 0.37 | 19 |
How this is worked out
volume in cubic feet = width in inches ÷ 12 × depth in inches ÷ 12 × length in feet
cubic yards = cubic feet ÷ 27
bags = cubic feet with waste ÷ what one bag yields, rounded up
At the dimensions above that is 17.78 cubic feet, which is 0.66 cubic yards.
What each bag size yields
| Bag size | cu ft | cu yd |
|---|---|---|
| 40 lb | 0.300 | 90 |
| 50 lb | 0.375 | 72 |
| 60 lb | 0.450 | 60 |
| 80 lb | 0.600 | 45 |
| 90 lb | 0.675 | 40 |
Questions
How much concrete do I need for 20 ft of 16 × 8 in footing?
0.66 cubic yards, which is 17.78 cubic feet before any waste allowance.
How many bags of concrete is that?
33 eighty-pound bags, or 44 sixty-pound bags, with 10% waste allowed for.
How much does that much concrete cost?
About $110 to $150 at $184 per cubic yard delivered. Prices vary by region, so enter a quote of your own to replace the default.
Is that a full truckload?
It is 1, once waste is allowed for. A full truckload is typically about 10 cubic yards.
This site works out quantities. It does not tell you what thickness, reinforcement or sub-base your job needs — those depend on local code and on the load.
Other calculators
Where these numbers come from
Bag yields: QUIKRETE Concrete Mix data sheet No. 1101. Price basis: Concrete Financial Insights weighted average selling price for 2025, escalated with U.S. Bureau of Labor Statistics PPI series PCU327320327320 (2026-06). Prices vary by region — enter your own quote above.