Concrete Yards Calculator
Concrete is the one material on the job you cannot top up cheaply. Order short and you get a cold joint in the middle of a slab; order long and you pay for a quarter yard nobody pours.
This concrete yards calculator for contractors takes a slab, a footing run or a round pier, returns cubic yards with your waste factor on top, rounds the order line up to the next quarter yard the way a plant bills it, and tells you how many truck loads that becomes. Thickness warnings reference IRC 2021 directly.
From poured volume to the number you give the plant
- Poured volume24 ft × 24 ft driveway at 5 in = 240 cu ft
- Into cubic yards240 ÷ 27 = 8.89 cu yd of finished concrete
- Waste on topAt 8 percent that becomes 9.60 cu yd
- Rounded to a quarter9.75 cu yd, and this is the order line
- Truck loadsOne load at a 10 cu yd loaded capacity
Every step after the first is an ordering decision rather than a geometry one. The quarter-yard rounding is how most plants bill, the waste percentage covers subgrade that is never perfectly flat, and a quarter of a yard costs far less than the cold joint you get when the last truck runs out mid-bay.
Yards, waste and truck loads in one pass
Pick the shape you are pouring, whether that is slab yardage, footing concrete yardage or a round pier, enter the dimensions, set your own waste percentage and the loaded capacity your supplier actually sends. The result separates the finished volume from the figure you should order, so you can see exactly what the waste allowance and the rounding are costing you.
Three numbers your dimensions cannot tell you
The geometry is the easy part. What turns a volume into a delivery is three figures that belong to your supplier and your site, not to the slab, and every one of them is left as an input here rather than assumed for you.
Your concrete waste factor
Five to ten percent is the common allowance, and it is covering subgrade variation more than spillage. A quarter-inch average over-dig across 1,000 sq ft is roughly 0.77 cu yd on its own, which is close to a quarter of a truck. Compacted, screeded subgrade earns the low end of that range.
What a truck actually carries
Drum ratings and legal delivery weight are different numbers. Mixer drums are commonly rated around 10 to 11 cu yd, but axle weight limits set by your state usually cap the load lower. Ask the dispatcher what they will put on a truck to your address rather than working from a published capacity.
Where short load starts
Most plants apply a minimum-load charge below a threshold, and the threshold and the fee are set per plant and per market. We publish neither as a figure because no primary source supports one. Get the number from your own supplier before you price the pour, not after the ticket arrives.
Order the rounded figure, not the exact one
The calculator returns both on purpose. The exact volume is what the slab will hold if the subgrade is perfect and nothing spills; the rounded quarter-yard line is what you order. Running short mid-pour means a cold joint where you did not plan one, a construction joint detail you have to defend to an inspector, and a second short-load charge on top. Planning the joints between loads to land on a control joint or a bulkhead removes most of that risk on multi-truck pours.
The IRC 2021 figures behind the thickness field
The calculator warns you when a thickness drops below a code minimum, so it is worth knowing where those minimums come from. All three are quoted from the 2021 International Residential Code at ICC Digital Codes, and the third one contradicts most of what is still published about slabs.
3½ in
IRC 2021 R506.1 sets the minimum thickness for concrete slab-on-ground floors, with expansive soils sent to R403.1.8 and the specified compressive strength set by R402.2. Anything thinner than this is outside the prescriptive path, whatever the driveway is carrying.
12 in × 6 in
R403.1.1 sets a minimum footing width of 12 in and a minimum depth of 6 in, with the width driven by the soil load-bearing value in Table R401.4.1 and projections of at least 2 in. The calculator warns on depth below 6 in; the 12 in width is on you to check.
10 mil
R506.2.3 calls for a 10-mil vapor retarder meeting ASTM E1745 Class A with joints lapped at least 6 in. Much of what is online still says 6 mil, which is the older requirement. Garages, carports, patios and unheated accessory structures are listed exceptions.
| IRC 2021 Table R402.2 — minimum specified compressive strength (f′c) | Negligible | Moderate | Severe |
| Basement walls, foundations and other concrete not exposed to the weather | 2,500 | 2,500 | 2,500 |
| Basement slabs and interior slabs on grade, except garage floor slabs | 2,500 | 2,500 | 2,500 |
| Basement, foundation and exterior walls and other vertical work exposed to the weather | 2,500 | 3,000 | 3,000 |
| Porches, carport slabs and steps exposed to the weather, and garage floor slabs | 2,500 | 3,000 | 3,500 |
Values are psi at 28 days. Weathering potential is a map, not a choice: it comes from IRC Table R301.2 for your jurisdiction. Where the table shows 3,000 or 3,500 the concrete must be air entrained at 5 to 7 percent total air by volume, and a steel-troweled garage floor may drop to 3 percent air only if the specified strength rises to at least 4,000 psi. That is why the same driveway detail can call for a different mix in a severe-weathering jurisdiction than in a negligible one, and why the psi line on the ticket is a code decision rather than a preference.
- IRC 2021 R402.2 and Table R402.2 — minimum specified compressive strength by weathering potential, air entrainment notes d and f, and the ACI 318 Section 19.3.3.4 limit on fly ash and other pozzolans in garage and deicing-exposed slabs.
- IRC 2021 R403.1.1 Minimum size — footings not less than 12 in in width and 6 in in depth, width per Table R401.4.1, projections not less than 2 in.
- IRC 2021 R506.1 General — slab-on-ground floors a minimum 3½ in thick, designed per this section or ACI 332.
- IRC 2021 R506.2.2 Base and R506.2.3 Vapor retarder — 4 in base course where the slab is below grade, and a 10-mil ASTM E1745 Class A retarder with 6 in lapped joints.
Code text read at ICC Digital Codes and figures checked 11 September 2026. We publish no short-load fee amount and no ready-mix truck capacity as a standard, because no primary industry source states either; both are user inputs with the truck field defaulting to a typical loaded figure you should overwrite. Supplier yield is governed by unit-weight testing to ASTM C138 rather than by anything this calculator can see.
Concrete ordering questions, answered
How many yards for a slab 24 by 24 at 4 inches?
7.11 cubic yards of finished concrete. A 4 inch slab holds 0.0123 cu yd per square foot, so 576 sq ft times 4 in is 192 cubic feet, divided by 27. Add your waste factor before ordering: at 8 percent it becomes 7.68 cu yd, and rounded up to the next quarter yard the order line is 7.75 cu yd, or one truck load.
What concrete waste factor percentage should I use?
Five to ten percent is the common allowance. It is mostly covering subgrade that sits lower than the string line rather than spillage, which is why a well-compacted and screeded base earns the bottom of the range and a rough over-dig earns the top. A quarter-inch average thickness error across 1,000 sq ft is about 0.77 cu yd by itself.
What concrete psi do I order for a driveway or a garage floor?
It depends on your weathering region, not on the pour type alone. IRC 2021 Table R402.2 requires 2,500 psi for porches, carport slabs, steps and garage floors in negligible-weathering areas, 3,000 psi in moderate and 3,500 psi in severe, with 5 to 7 percent air entrainment where 3,000 or higher applies. Check Table R301.2 for your jurisdiction before defaulting to 3,000 everywhere.
What is a short-load charge on ready-mix concrete?
A minimum-load fee applied when an order falls below a plant threshold, charged on top of per-yard pricing. Under about 3 cubic yards most suppliers apply one, and under 1 cubic yard many will not deliver at all. Thresholds and fees are set per plant and per market, so ask your supplier for their own numbers rather than working from a published figure.
How many cubic yards per truck does ready-mix concrete deliver?
Standard rear-discharge drums are commonly rated around 10 to 11 cubic yards, but the legal axle weight for your state usually caps a delivery below the drum rating. Treat capacity as an assumption you confirm with the dispatcher, which is why the calculator leaves it as a field rather than fixing it at a single national number.
Why did my pour come up short of the ticket?
Usually the subgrade, occasionally the batch. Compare the placed volume against the delivery ticket: yield is governed by unit-weight testing to ASTM C138, and a batch can run short when water or air content drifts. Before blaming the plant, measure your actual average thickness, because a quarter-inch of over-dig across a large slab accounts for most short pours.
A concrete crew is only as busy as the phone
Takeoff accuracy protects the margin on the work you already have. It does not put another driveway, footing or slab on next month's schedule, and that is a different problem with a different fix.
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Zayn founded Zainfy in 2023 and has spent six years in performance marketing for home remodeling and construction companies across the United States. He built this tool set because the contractors he works with were losing more money to pricing and takeoff math than to any advertising decision.
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