Concrete Calculator

Calculate cubic yards of concrete needed for slabs, footings, columns, and walls. Includes waste factor and cost estimation.

How it works

Concrete (cubic yards) = Length(ft) × Width(ft) × Depth(ft) / 27. 80-lb bags per yard ≈ 40; 60-lb ≈ 60.

Worked example

A 10×10 ft slab, 4 in thick = 100 × 0.333 / 27 ≈ 1.23 cubic yards ≈ 49 bags of 80-lb concrete.

Frequently asked questions

How do I calculate the number of bricks needed for a wall including mortar joints?

Bricks per m² of wall ≈ 60 for a standard 215×102.5×65 mm brick with a 10 mm mortar joint. Multiply by wall area, then add 5–10% for cuts and breakage.

Is it cheaper to mix my own concrete or buy pre-mixed bags?

For jobs under about 1 cubic yard, bags are cheaper and simpler. Above 1 cubic yard, a ready-mix truck is usually cheaper per yard and vastly less labour — the break-even is around 1–1.5 cubic yards.

How thick should a concrete slab be?

Patios and walkways: 4 inches. Driveways for cars: 4 inches on compacted base. Driveways for trucks/RVs: 5–6 inches with rebar. Garage floors: 4–6 inches depending on load.