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Concrete & Masonry

Concrete Calculator

Calculate exactly how much concrete you need for a slab, footing, or column — in cubic yards, cubic feet, and premixed 60lb or 80lb bags.

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Slab Dimensions

Result


Enter dimensions to calculate concrete needed
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Disclaimer: This calculator provides an estimate for planning purposes only and is not engineering advice. Always add 5-10% extra for waste/spillage and consult a structural engineer or contractor for load-bearing or code-critical pours.

About the Concrete Calculator

Ordering the right amount of concrete avoids costly re-orders or wasted material. This calculator computes the volume of concrete needed for a rectangular slab, footing, or pad based on its length, width, and depth.

Ready-Mix vs. Bagged Concrete

For larger pours, concrete is typically ordered by the cubic yard from a ready-mix truck. For smaller DIY jobs, premixed bags (60lb or 80lb) are more practical — this tool converts your total volume into both units so you can choose the right approach.

Why Add a Waste Allowance

Ground isn’t perfectly level, forms can shift, and some material is always lost during mixing and placement. A 5-10% waste allowance is standard practice to avoid running short mid-pour.

Frequently Asked Questions

One cubic yard of concrete requires approximately 45 bags of 80lb premixed concrete (each 80lb bag yields about 0.6 cubic feet, and there are 27 cubic feet in a cubic yard).
For pours larger than about 1 cubic yard, ready-mix delivery is usually more cost-effective and less labor-intensive than mixing dozens of bags by hand. For smaller jobs like fence posts or small pads, bagged concrete is more practical.
Uneven ground, form shifting, and spillage during mixing/placement typically use 5-10% more material than the theoretical volume. Skipping this allowance is the most common reason DIYers run short mid-pour.
Typical guidance is 4 inches for walkways and patios, and 5-6 inches for driveways that need to support vehicle weight. Always check your local building code for load-bearing requirements.
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