Concrete calculator

Order the right amount: volume in cubic yards and meters with waste allowance, ready-mix cost, and bag counts for 40, 60, and 80-pound mixes.

How to Concrete calculator

1. Step 1. Choose the pour shape: slab, footing, or column.
2. Step 2. Enter dimensions in feet/inches or meters/centimeters.
3. Step 3. Add a waste allowance (5–10% is standard).
4. Step 4. Review volume, bag counts, and estimated delivery cost.

Frequently asked questions

How many yards of concrete for a 20×20 slab?

A 20×20 ft slab at 4 inches thick is about 4.94 cubic yards; with 10% waste allowance, order ~5.5 yards — the calculator handles this instantly.

How thick should a concrete slab be?

4 inches for patios and walkways, 5–6 inches for driveways carrying vehicles, per common residential practice.

How many 80-lb bags make a yard?

About 45 bags (each yields ~0.6 cu ft; a yard is 27 cu ft). Bags suit small pours; ready-mix trucks are better beyond ~1 yard.