Estimate slab volume, ready-mix quantity, bag count, and material cost for concrete pours in US and UK units.
This concrete calculator provides planning estimates only. Actual order quantities vary by mix design, reinforcement, sub-base, waste, delivery minimums, and site conditions. Always confirm dimensions and ordering with your supplier or contractor before purchasing materials.
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Concrete is ordered by volume, so the first step is to calculate the space you are filling. For a slab or footing, multiply length × width × thickness in the same units, then convert to cubic yards (the standard US unit) or cubic metres. Because thickness is usually in inches, convert it to feet first — a 4-inch slab is 0.333 ft thick.
For round columns or footings, use the volume of a cylinder: π × radius² × height. The calculator handles slabs, footings and columns and totals the volume for you, including a recommended allowance for waste.
For small jobs, bagged concrete is convenient: roughly 45 × 80 lb bags, 60 × 60 lb bags, or 90 × 40 lb bags make one cubic yard. For anything larger than about a cubic yard, ready-mix delivery is usually cheaper and avoids cold joints from mixing in stages.
Always order 5–10% extra to cover spillage, uneven sub-grade and over-excavation. Running short during a pour creates a weak seam where fresh concrete meets set concrete, so a small surplus is far safer than ordering the exact calculated amount. Have your forms braced and your crew ready before delivery, since concrete begins to set quickly.
Multiply length × width × thickness in the same units to get the volume, then convert to cubic yards or cubic metres. The calculator does this and adds a recommended waste margin.
It depends on bag size: roughly 45 × 80 lb bags, 60 × 60 lb bags, or 90 × 40 lb bags make one cubic yard. The calculator converts your volume into a bag count.
Add about 5-10% for spillage, uneven subgrade and over-excavation. Running short mid-pour creates a cold joint, so a small surplus is safer than ordering exactly the calculated amount.
Yes. Enter the dimensions of the shape — rectangular slabs, footings, or round columns (using diameter and height) — and it returns the volume of concrete required.