How Much Concrete Do You Need?
Calculate cubic yards of concrete for slabs, footings, columns, and stairs. Includes bag count and cost estimate.
How to Calculate Concrete Volume
Concrete is sold by the cubic yard. The formula: Length (ft) × Width (ft) × Depth (ft) ÷ 27 = cubic yards. A standard 4-inch thick slab covering 200 square feet needs: 200 × 0.333 ft ÷ 27 = 2.47 cubic yards. Always add 10% for waste, spillage, and uneven subgrade.
Bags vs. Ready-Mix Truck
For small projects (under 1 cubic yard), pre-mixed bags are practical. One 80-lb bag yields about 0.6 cubic feet. A 10×10 patio at 4 inches needs roughly 56 bags — a full day of mixing. For anything over 1-2 cubic yards, order a ready-mix truck ($150-175 per yard delivered). It saves enormous time and produces a more consistent pour.
Concrete Thickness Guidelines
Sidewalks: 4 inches. Patios: 4 inches. Driveways (cars): 4-5 inches. Driveways (trucks/RVs): 5-6 inches. Garage floors: 4-6 inches. Footings: typically 12 inches deep, width varies by load. Going thinner than recommended leads to cracking under load.
The most common DIY concrete mistake: ordering too little. Concrete cannot be "added later" — the cold joint between pours is a permanent weakness. Order 10% more than calculated and send back what you do not use.
