Concrete Calculator
Calculate the concrete volume needed for slabs, columns, footings, stairs and other common construction shapes — in cubic yards or cubic meters.
How to use the Concrete Calculator
- Enter your inputs into the Concrete Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
The concrete volume formulas
Slab: L × W × thickness · · · Column: π × r² × h · · · Footing: L × W × D · · · Stair: tread area × number
Each pour type has its own volume calculation. Add 5–10% to total volume to account for spillage, over-excavation and form irregularities.
Worked example
A 20 ft × 12 ft × 4 in slab: 20 × 12 × (4/12) = 80 cubic feet = 2.96 cubic yards. Round to 3 yards plus 10% waste = 3.3 yards ordered.
Frequently asked questions
How do I order concrete?
Concrete is sold by the cubic yard in the US, cubic meter elsewhere. Order in 0.25 yard increments minimum. Most ready-mix trucks carry 9–10 yards.
How much should I order over my calculation?
5–10% extra is standard for over-pour, spillage and irregular sub-grade. Running short mid-pour is much worse than having a bit left over.
What is PSI for concrete?
Compressive strength rating. Common: 3,000 PSI for residential slabs and footings; 4,000+ for driveways and structural applications. Stronger concrete costs more but is far less likely to crack.