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Cubic yards of ready-mix for slabs, footings, grade beams, columns and caissons, with waste and cost.

How it works

Ready-mix is sold by the cubic yard, which is 27 cubic feet. For a slab, multiply length and width in feet by the thickness converted to feet. A footing or grade beam works the same way with its width and depth in inches. A round column or caisson is π × radius² × height. Add a waste allowance, typically 5–10%, for uneven subgrade, spillage and what stays in the chute.

cubic yards = length (ft) × width (ft) × (thickness (in) ÷ 12) ÷ 27
27
Cubic feet in a cubic yard
÷ 12
Converts inches to feet
π r² h
Volume of a round column, with r = diameter ÷ 2
waste
5–10% is standard; more on rough ground

Worked example

A 20 × 20 ft slab, 4 inches thick, with 10% waste, at $165 a yard.

  1. 1Volume: 20 × 20 × (4 ÷ 12) = 133.3 ft³
  2. 2With waste: 133.3 × 1.10 = 146.7 ft³
  3. 3Cubic yards: 146.7 ÷ 27 = 5.43 yd³
  4. 4Cost: 5.43 × $165 = $896

Order 5.5 yd³ of ready-mix, about $900 before delivery fees.

Frequently asked questions

How thick should a concrete slab be?

Four inches is standard for patios, walkways and garage floors carrying cars. Driveways are usually 5–6 inches, and slabs under heavy trucks or equipment are 6–8 inches, often with rebar. Thicken the edges of a slab that is not supported by a footing to 8–12 inches around the perimeter.

How much does a yard of concrete cost?

Ready-mix commonly runs $140–$200 per cubic yard in the US in 2026, depending on strength, region and additives such as fibre or accelerators. Small orders under 4–6 yards usually carry a short-load fee, and trucks charge standby time if the site is not ready when they arrive.

Should I use bags or ready-mix?

Below about one cubic yard, bags are usually cheaper and easier; one yard takes about 45 bags of 80 lb. Above that, a ready-mix truck saves hours of mixing and gives a more uniform pour. For in-between jobs, many suppliers rent a towable mixer trailer that holds about a yard.

How much concrete fits in a truck?

A standard ready-mix truck carries 8–10 cubic yards, and some carry up to 11. Large pours are scheduled as a series of trucks spaced so the concrete arrives continuously, without one truck waiting on the last.

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