This free concrete calculator instantly figures out how much concrete you need — in cubic yards, cubic feet, and bags — for slabs, footings, columns, tubes, and stairs.
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Select your project shape — slab, footing, column, tube/pier, or stairs — then enter your dimensions. Choose your measurement system (imperial or metric), adjust the waste factor slider to account for spillage and over-ordering, select your bag size, and click Calculate. The tool instantly returns cubic yards, cubic feet, cubic meters, and the number of pre-mixed bags you'll need, and the diagram above updates with your actual dimensions.
Concrete is unforgiving. Under-order and you end up with cold joints — a structural weak point where old concrete meets new. Over-order and you're paying $150+ per cubic yard for concrete you'll shovel into a dumpster. A typical 10×12 foot driveway pad at 4 inches thick needs about 1.5 cubic yards. That's around $225–$350 delivered. Ordering even half a yard too much on a large pour (say, a 40-foot foundation footing) can waste $75–$100.
Contractors and homeowners use this concrete calculator before calling ready-mix plants, estimating material costs for bids, pulling permits, and planning how many bags to buy for smaller DIY jobs. A 10×10 patio at 4 inches thick takes about 56 bags of 80 lb mix without any waste factored in — knowing that before you load up your car matters.
The waste factor is critical. Most professionals add 5–10% for residential pours and up to 15–20% for irregular shapes, sloped forms, or when mixing by hand where some inevitably gets stuck in the mixer drum.
All shapes convert dimensions to feet, compute volume in cubic feet, then convert to cubic yards (÷ 27) and cubic meters (× 0.0283168).
The stringer-supported formula only estimates the tread wedges that sit on top of an existing support structure, so it will understate material needed for a fully solid staircase. Choose "solid pour to grade" if there's nothing but compacted fill or ground beneath your steps — it fills the entire stepped void down to grade.
With waste: Final Volume = Raw Volume × (1 + Waste% ÷ 100). Bags needed = Final cubic feet ÷ cubic feet per bag (0.30 for 40 lb, 0.45 for 60 lb, 0.60 for 80 lb), rounded up.
Say you're pouring a 10 ft × 10 ft slab at 4 inches thick, using 80 lb bags, with a 10% waste factor.
Without any waste factor, the same slab needs 33.33 ÷ 0.60 = 55.5 → 56 bags. That 6-bag gap is your cushion for an uneven subgrade, spillage, and forms that aren't perfectly plumb.
A 10×10 slab at 4 inches thick = 33.3 cubic feet = about 1.23 cubic yards without waste. Without any waste factor you'd need 56 bags of 80 lb concrete mix; with a 10% waste factor (recommended for most DIY pours) that rises to about 62 bags. At $6–$8 per bag, expect $370–$500 in material alone — at which point ready-mix delivery is often cheaper and easier.
Residential driveways should be at least 4 inches thick for passenger vehicles, and 5–6 inches for trucks, SUVs, or areas where heavy vehicles park. Thicker slabs dramatically increase load capacity. Use this calculator with different thickness values to compare the volume difference.
A cubic yard of concrete weighs approximately 4,050 pounds (about 2 tons). This matters when planning deliveries — ready-mix trucks typically carry 8–10 cubic yards, and your driveway or job site must be accessible for a vehicle of that weight.
Yes — select "Metric" in the measurement system dropdown, and the calculator accepts meters (for length/width/height) and centimeters (for thickness/depth). Results are still shown in cubic yards, cubic feet, and cubic meters so you can compare across systems.
Concrete stairs can be built two very different ways. If steps rest on stringers or a formed support structure, you only need to pour the tread wedges — a much smaller volume. If the stairs are poured as one solid monolithic block directly on grade or fill, you need concrete filling the entire stepped void down to the ground, which can be several times more material. Toggle the "solid pour to grade" checkbox to switch between the two formulas.
Ready-mix concrete typically costs $150–$180 per cubic yard delivered in most U.S. markets, plus a short-load fee (often $60–$100) if you order less than a full truck (usually under 3–5 cubic yards). Bagged concrete mix is more expensive per cubic foot but has no minimum order, which is why it usually makes sense for volumes under about half a cubic yard.
Calculator by Toolwick