Concrete Calculator: Cubic Yards, Bags & Cost

Calculate the concrete volume for a rectangular slab from its length, width, and thickness. See cubic yards, cubic feet, and cubic meters. Optionally estimate whole bags using your product's labeled yield, or material cost using a price per volume unit.

Calculate concrete for a rectangular slab

Enter the planned dimensions. Thickness is an input, not a recommendation: this calculator does not design a structural slab, foundation, or reinforcement.

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How to calculate concrete yards

Cubic yards = length (ft) x width (ft) x thickness (in) / 324

The divisor converts inches to feet and cubic feet to cubic yards: 12 x 27 = 324. A slab 9 feet long, 9 feet wide, and 4 inches thick has a geometric volume of 1 cubic yard, or 27 cubic feet. The thickness here is an arithmetic example, not a design recommendation.

Concrete bags depend on labeled yield

Bag equivalents = required volume / mixed concrete yield per bag. Round up to whole bags.

If the product you select states a yield of 0.6 cubic feet per bag, 27 / 0.6 = 45 bags for one cubic yard, before any extra allowance. A product with a different yield requires a different bag count. Do not substitute pounds or kilograms for cubic feet or liters.

Metric concrete volume

Cubic meters = length (m) x width (m) x thickness (cm) / 100

A 5 m by 4 m slab at 10 cm thickness has a geometric volume of 2 cubic meters. With a stated yield of 20 liters per bag, 2,000 / 20 = 100 bags. Use the manufacturer's actual yield, not this example as a default.

Concrete cost example

Material cost = volume x price per matching volume unit. At an illustrative price of $150 per cubic yard, one cubic yard costs $150 for material. This is not a current market quote or a total installed slab cost.

Frequently asked questions

Are square yards and cubic yards interchangeable?

No. Square yards measure surface area; cubic yards measure volume. You must include thickness to estimate concrete. For example, 9 square yards of area does not mean 9 cubic yards of concrete.

Does the calculator choose a slab thickness?

No. Required thickness, concrete specification, base preparation, and reinforcement depend on the project and applicable design requirements. Use a qualified professional where needed.

Does this calculate concrete for blocks, footings, or round columns?

This version estimates a solid rectangular volume only. Hollow blocks require a product-specific fill volume; columns and other shapes need their own geometry. Do not use external block dimensions as if they were solid fill.

Is extra concrete included?

No percentage is added. Whole-bag rounding is separate from any allowance. Ask your supplier or contractor how site conditions, handling, and purchasing increments affect the final order.

What happens when I switch units?

The dimensions clear so feet are not accidentally used as meters. Bag yield and price retain their own explicitly selected units and values.

Which inputs are supported?

Positive dimensions, up to 10,000 for length and width and 1,000 for thickness in displayed units. Optional yield must be positive and no more than 10,000 cubic feet or liters per bag. Optional price can be from $0 to $1,000,000 per selected volume unit. Up to four decimals are accepted, with a decimal point or comma and no thousands separators.

Related measurement tools

For area only, use our Square Footage Calculator. For loose landscaping material, see the Gravel Calculator.

HandyMetric provides general estimation tools, not structural engineering, construction specifications, or installation services. Verify dimensions and purchasing requirements before ordering.