How to Calculate Concrete Volume

This concrete calculator computes the exact volume of concrete needed for slabs, footings, and columns in cubic yards, cubic feet, and cubic meters. The core formula for rectangular shapes: Volume (ft³) = Length (ft) × Width (ft) × Depth (in) ÷ 12. Divide by 27 to convert to cubic yards (the standard ordering unit for ready-mix concrete). Always add 10% waste to account for spillage, uneven subgrade, and settling.

Ready-Mix vs. Bagged Concrete

For projects under 1 cubic yard (27 ft³): use bagged concrete. A 60-lb bag covers ≈0.45 ft³; an 80-lb bag ≈0.6 ft³. For projects 1–3 yd³: consider renting a concrete mixer and using bulk dry concrete. For projects over 1 yd³: ready-mix concrete trucks offer 3,000–4,000 PSI concrete delivered and poured at approximately $125–$200/yd³. Short-load fees apply for small orders.

Concrete Thickness Guidelines

Driveway (cars): 4 inches minimum. Driveway (trucks/RVs): 5–6 inches. Patio/walkway: 3.5–4 inches. Garage floor: 4–6 inches. Structural footings: minimum 8 inches deep. Basement walls: 8–10 inches. Higher PSI concrete (3,500–5,000) is recommended for driveways and areas with freeze-thaw cycles. Use rebar (#4 or #5 bar) on a 2-foot grid for driveways; wire mesh for patios.

Estimating Cost

Ready-mix concrete: $100–$200/yd³ delivered (varies by region and mix spec). Bags: 80-lb bags at $6–$8 each; cost per yd³ ≈ $270–$360. Labor: $2–$5/ft² for a typical slab pour. Pumping (if needed): $500–$1,500 for pump truck. Reinforcement: rebar $0.25–$0.50/lb; wire mesh $0.10–$0.20/ft². Finishing and sealing: $1–$2/ft² additional. Related tools: Area Calculator, Volume Calculator.