Concrete Calculator — Cubic Yards & Bags Needed
Estimate concrete volume for any pour. Enter your shape and dimensions to get cubic yards, plus the equivalent count of pre-mix bags in either 60-lb or 80-lb sizes.
Results are estimates based on the dimensions and specifications you provide. Actual material needs may vary based on project conditions, material waste, and installation method. Always consult with a professional for complex projects.
Wet concrete is highly alkaline and can cause severe skin and eye burns. Always wear waterproof gloves, eye protection, and long sleeves. Larger structural pours typically require permits and engineering review.
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How this calculator works
For slabs and footings we compute volume as length × width × thickness in cubic feet, then convert to cubic yards (÷ 27). For tube-shaped footings we use π × r² × height. A 60-lb bag of concrete pre-mix yields about 0.45 cu ft when mixed, and an 80-lb bag yields about 0.6 cu ft. We recommend ordering ready-mix at 10% over your calculated volume to account for over-excavation and spillage.
More about this calculator
Concrete is one of the easiest materials to under-order and one of the hardest to add to mid-pour. A typical 4-inch slab measuring 10 × 10 ft requires about 1.23 cubic yards — call it 1.4 cubic yards on the truck order to allow for uneven excavation and a generous fill.
For small DIY projects, pre-mix bags are convenient up to about 1 cubic yard. Beyond that, ordering a ready-mix delivery becomes faster and cheaper. Most ready-mix companies have a 1 cubic yard minimum and a short-load fee for orders under 3 cubic yards.
Thickness rules of thumb: 4 inches for sidewalks and patios, 6 inches for driveways, 8 inches for footings under most residential walls. For unheated outdoor pours, place welded wire mesh or rebar to control cracking.
Frequently asked questions
About 45 bags of 80-lb pre-mix make one cubic yard. For 60-lb bags, plan on around 60 bags per cubic yard.
Yes — order 10% more than your calculated volume. It’s cheaper to slightly over-order than to halt a pour halfway through.
4 inches for sidewalks and patios, 5–6 inches for driveways with vehicle traffic, 8+ inches for heavy-load areas. Local building codes may require minimum thicknesses for footings.
Use bagged pre-mix for projects under about 1 cubic yard. Above that, ready-mix delivery is faster, cheaper per yard, and produces a more consistent pour.