Calculate cubic yards of concrete for slabs, footings, and column piers. Enter dimensions, select your waste factor, and get cubic yards plus 80 lb bag count.
Concrete forms, screed rails, and vibrators keep your pour clean and on spec. Shop concrete tools at Express Tools.
Shop Express Tools →Concrete volume estimation is a core takeoff task for any contractor. Over-ordering wastes money; under-ordering causes cold joints and schedule delays. This calculator handles the three most common pour shapes: flat slabs (garage floors, driveways, sidewalks), continuous or pad footings (foundation walls, grade beams), and round column piers (sonotubes, drilled piers, deck footings). Always apply a waste factor — 5% minimum for slabs with tight formwork, 10% for footings where soil conditions or form gaps may cause loss. Bag estimates assume standard 80 lb bags at 0.6 cu ft yield.
Save this calculation to a Sitemark job →
Log calculations with GPS location, timestamp, and job context. Auto-generates field reports.
Start free trialMultiply length (ft) × width (ft) × thickness (in ÷ 12) to get cubic feet, then divide by 27 to get cubic yards. A 20×20 ft slab at 4 inches thick = 20 × 20 × (4/12) / 27 = 4.94 CY.
An 80 lb bag of ready-mix concrete yields approximately 0.6 cubic feet. Since there are 27 cubic feet in a cubic yard, you need about 45 bags per cubic yard. Always add 5–10% waste factor.
Use 5% for poured slabs with clean forms. Use 10% for footings, piers, and irregular pours where spillage and form seepage are more likely. Precast and pump pours typically use 5%.
Volume = π × (diameter/2)² × height. For a 12-inch diameter pier 4 ft tall: π × (0.5)² × 4 = 3.14 cu ft = 0.12 CY. Use the column mode in this calculator for instant results.
For pours over about 1 cubic yard, ready-mix concrete is more economical and consistent. For small jobs under 0.5 CY — like a single fence post or small footing — bags are practical. Always add waste factor to your order.
Calculate concrete volume in cubic yards for slabs, footings, and columns/piers.