Concrete Calculator
Calculate how much concrete you need for slabs, footings, columns, and walls. Enter your project dimensions and choose between bulk cubic yards or bagged concrete for instant results.
How to Calculate Concrete
The concrete volume formula converts your project dimensions into cubic yards:
- Measure the area you want to pour in feet (length and width).
- Determine the thickness in inches. Standard slabs are 4 inches thick.
- Calculate volume: Length (ft) × Width (ft) × Depth (in) ÷ 12 ÷ 27 = Cubic Yards.
- Convert to bags: Divide cubic yards by the yield per bag to get the number of bags needed.
Concrete Thickness Guide
- 4 inches: Sidewalks, patios, shed floors, and standard slabs
- 6 inches: Driveways, garage floors, and areas with vehicle traffic
- 8 inches: Foundation walls and structural elements
- 12 inches: Footings, load-bearing foundations, and columns
Concrete Types and Uses
- Standard mix (2,500 PSI): General-purpose use for walkways and patios
- Crack-resistant (4,000 PSI): Driveways and garage floors
- High-strength (5,000+ PSI): Footings, foundations, and structural work
- Fast-setting: Post holes, small repairs, and cold-weather pours
Frequently Asked Questions
How much concrete do I need?
To calculate concrete needed: multiply length × width (in feet) × depth (in inches), divide by 12 to convert to feet, then divide by 27 to get cubic yards. For example, a 10ft × 10ft slab at 4 inches deep needs about 1.23 cubic yards of concrete.
How many bags of concrete for a 10x10 slab?
A 10×10 foot slab at 4 inches thick requires approximately 1.23 cubic yards of concrete. That equals about 56 bags of 80lb concrete mix, 72 bags of 60lb mix, or 112 bags of 40lb mix. For slabs this size, ordering ready-mix concrete is often more practical.
How much does concrete cost per yard?
Ready-mix concrete typically costs $125-$165 per cubic yard delivered, depending on your location and the mix type. Bagged concrete costs more per yard — roughly $250-$350 per cubic yard when buying 80lb bags. For projects over 1 cubic yard, ready-mix is usually more economical.
How thick should a concrete slab be?
Standard concrete slab thickness: 4 inches for patios, sidewalks, and shed floors; 6 inches for driveways and garage floors; 8-12 inches for footings and structural foundations. Always check local building codes for minimum requirements.