Concrete Volume Calculator

Multiply the slab's length × width × thickness. In imperial units, if length and width are in feet and thickness is in inches, divide the thickness by 12 to convert to feet first. The formula is: Volume (ft³) = Length (ft) × Width (ft) × Thickness (in) ÷ 12. Then divide by 27 to get cubic yards — the standard unit for ordering concrete in the US. One cubic yard equals 27 cubic feet. For metric, use meters for length/width and convert thickness from cm to meters (÷100).

One cubic yard of concrete requires approximately: 45 bags of 80 lb concrete, 60 bags of 60 lb concrete, or 90 bags of 40 lb concrete. Each 80 lb bag yields about 0.022 cubic yards (0.6 ft³). For small DIY projects under 1 cubic yard, bagged concrete is convenient. For larger projects, ready-mix truck delivery is usually more cost-effective and saves significant labor.

A wastage factor of 5–10% is standard in the construction industry. This accounts for spillage, uneven ground, formwork irregularities, over-excavation, and slight miscalculations. For critical structural work, some engineers specify up to 10% wastage. Always round up and order a bit extra — it's far cheaper than running short mid-pour. Our calculator lets you adjust the wastage percentage with the slider above.

For a round column, use: Volume = π × (diameter ÷ 2)² × height. In imperial: if diameter is in inches and height in feet, convert diameter to feet first (÷12). Formula: Volume (ft³) = π × (D_in ÷ 24)² × H_ft. For a square column: Volume = side² × height. Our calculator handles both shapes — simply select Round or Square, enter your dimensions, and get instant results in cubic yards or cubic meters.

A slab is a flat horizontal concrete surface (like a patio, driveway, or floor) where the thickness is relatively small compared to the length and width. A footing (or foundation footing) is a structural element that transfers building loads to the soil — it's typically deeper and narrower, running continuously under walls (strip footing) or as isolated pads under columns. The volume calculation formula is the same (L × W × D), but footings usually involve trenches and may require more precise depth control.

A standard concrete mixer truck carries 8 to 10 cubic yards of ready-mix concrete. Some larger trucks can carry up to 12 yards, but 9–10 yards is the most common full load. If your project requires more than one truckload, plan for coordinated deliveries to avoid cold joints between pours. For projects under about 1 cubic yard, bagged concrete mixed on-site is typically more practical.

As a general rule: Under 1 cubic yard (approx. 45 bags of 80 lb) — bagged concrete is practical for DIY. 1–3 cubic yards — either option works; bagged is labor-intensive but gives you flexibility. Over 3 cubic yards — ready-mix truck delivery is strongly recommended for consistency, time savings, and overall cost-effectiveness. Our calculator shows bag estimates so you can make an informed decision.

This calculator's Slab mode is designed for rectangular slabs. For a circular slab (like a round patio), use the Column calculator in Round shape mode — the volume formula is the same: π × radius² × thickness. Just enter the circle's diameter and the slab thickness as the height. The math works identically for any cylindrical concrete element.

Patios & walkways: 4 inches (10 cm)
Driveways: 5–6 inches (13–15 cm)
Garage floors: 6 inches (15 cm)
Footings: 6–12 inches (15–30 cm) wide, 6–24 inches deep depending on frost line and load
Structural columns: 8–24 inches (20–60 cm) diameter or side, depending on load