Concrete Slab Calculator
Estimate concrete and bags for a flat slab.
How It Works
Volume (ft³) = Length × Width × (Thickness ÷ 12). Cubic yards = Volume ÷ 27.
Example
A 12 ft × 12 ft garage slab at 4 in thick: 12 × 12 × (4 ÷ 12) = 48 ft³ ≈ 1.78 cubic yards before waste.
Frequently Asked Questions
What thickness do I need?
4 in for most patios and walkways, 4–6 in for driveways, and 6 in or more for vehicle-heavy or load-bearing slabs.
Should I add rebar or mesh?
Most residential slabs use welded wire mesh or rebar on edges. Check local codes — it does not change the concrete volume.
How much does a concrete truck hold?
Typical trucks carry 9–10 cubic yards. If your slab is under that, you may pay a short-load fee.