Concrete Calculator
Calculate how much concrete you need for slabs, footings, columns, and other projects. Get results in cubic yards, cubic feet, and pre-mixed bags.
How to Calculate Concrete for Your Project
Estimating concrete accurately prevents costly over-ordering and frustrating shortages mid-pour. The basic formula is straightforward: multiply the length, width, and depth of your project area to get the total volume, then add a waste factor to account for spillage, uneven sub-grades, and form variations.
Concrete Calculator Formula
For rectangular slabs and footings, the formula is: Volume (cubic feet) = Length (ft) x Width (ft) x Depth (in) / 12. To convert cubic feet to cubic yards, divide by 27. For round columns and sonotube forms, use: Volume = π x radius² x height.
How Much Does Concrete Cost?
Ready-mix concrete typically costs between $120 and $200 per cubic yard depending on your location and the mix design. For small projects, pre-mixed bags are more practical: a 60-lb bag covers about 0.45 cubic feet and costs $4-6, while an 80-lb bag covers about 0.6 cubic feet and costs $5-8. For projects requiring more than 1-2 cubic yards, ordering a ready-mix truck is usually more economical.
Tips for Ordering Concrete
- Always add 10% extra for waste — more for irregular shapes or slopes
- For slabs, a standard depth is 4 inches for patios and walkways, 6 inches for driveways
- Ready-mix trucks typically carry 8-10 cubic yards; order at least 1 yard per truck for delivery
- Consider the weather — concrete should not be poured when temperatures drop below 40°F
Common Concrete Projects
A typical 10x10 patio at 4 inches deep requires about 1.25 cubic yards. A 20x20 two-car driveway at 6 inches deep needs around 7.5 cubic yards. Deck footings using 12-inch sonotube forms at 4 feet deep require about 3.14 cubic feet per footing.