Concrete › Concrete yards calculator
Concrete yards calculator: how many cubic yards do I need, and how many trucks?
Enter a slab, patio or driveway by length, width and thickness, a footing by run, width and depth, or a round pier by diameter and depth, pick the mixer truck size, and get the concrete in cubic yards with waste inside, the ready-mix order rounded up to the next quarter yard, the number of truck loads, and a short-load prompt when the order is small. Free, no signup, printable.
Cubic yards = length × width × thickness, all three in feet, divided by 27. The default 20 × 10 ft slab at 4 in is 200 × ⅓ = 66.67 cubic feet, 2.47 cubic yards by the formula and 2.72 with the 10 percent waste the tool adds, so the order line rounds up to 2.75 cubic yards, one load on a 10-yard truck, and the tool notes that an order under about 3 yards usually carries a short-load surcharge. A cubic yard is 27 cubic feet and covers 81 sq ft at 4 in; the square-feet table runs both directions.
The calculator works the order side: rounding, truck loads and the plant's thresholds. It does not count bags, pick a slab thickness or subtract a post from a hole. For bags use the bags of concrete calculator, for thickness by use the concrete slab calculator, and for a post in the hole the post hole concrete calculator.
How to use this concrete yards calculator
What are you pouring? has three settings, and the fields change with it. Slab, patio or driveway takes length and width in feet and inches, so 12 ft 6 in can be typed as 12′ 6″ or 12.5, plus a thickness in inches in half-inch steps. Footing or trench takes the total run in feet, the footing width in inches and the footing depth in inches, and treats the trench as a rectangle the full length of the run: a 30 × 20 ft building is a 100 ft run, which the concrete footing calculator builds from the footprint and the soil. Round column, pier or hole takes a diameter in inches and a depth in feet and inches, as solid concrete; nothing is taken out for a post, a tube wall or a pipe. How many of these? multiplies the shape before anything is rounded, so eight piers are one entry and the order is rounded once for all of them.
Mixer truck capacity is the loaded figure your plant sends, 8, 9, 10 or 11 cubic yards, and only changes the truck-load count. Waste allowance defaults to 10 percent and is added to the volume once, before the order is rounded, which is why the default slab prints 2.72 cu yd, 73.33 cu ft and an order of 2.75 rather than 2.47, 66.67 and 2.5. Every result prints its assumptions and saves as a PDF; how every figure on this site is checked is on the methodology page.
| Row | What it is | Waste inside? |
|---|---|---|
| Concrete needed | Cubic yards of the shape, times the quantity, with the waste added; the headline | Yes |
| Ready-mix order (¼ yd steps) | The headline rounded up to the next quarter yard; only shown once the volume reaches half a yard | Already inside |
| Cubic feet | The same volume before dividing by 27 | Yes |
| Cubic metres | The same volume × 0.0283, for a plant that batches metric | Yes |
| Truck loads | The order line divided by the truck size you picked, rounded up | From the order |
| Area or Run length | Square feet of slab, or feet of footing run, times the quantity; nothing in round mode | No |
| Each | Only when the quantity is above one: cubic yards for a single shape, with waste | Yes |
What the calculator warns and notes
Two warnings, both from the residential code and both quoted further down: a slab under 3½ in is thinner than the IRC 2021 R506.1 minimum for a concrete floor, and a footing depth under 6 in is below the R403.1.1 minimum. The volume is still printed, because a 2 in topping or a shallow pad is a real job; the warning says the shape you typed would not pass as a floor or a footing. Round mode warns about nothing, since a pier has no minimum in the tool.
Three notes follow the order. Under 1 cubic yard the tool says most plants treat the job as a short load and many will not deliver it, and the order line itself disappears below half a yard, so a single post hole prints a volume and no truck line, on purpose. Under about 3 yards it flags the usual short-load surcharge zone. When the order needs more than one truck it names the count and tells you to plan the joint between loads at a control joint or a bulkhead. The last line is the same on every result: order the rounded quarter-yard figure, not the exact one, because running short mid-pour is far more expensive than a wasted quarter yard.
How to calculate concrete yards by hand: the formula for each shape
Every yardage figure is the volume in cubic feet divided by 27, and the only trap is the thickness, which is measured in inches and has to go into the formula in feet. Use the exact fraction: 4 in is ⅓ ft, 5 in is 5⁄12, 6 in is ½, 8 in is ⅔. Rounding 4 in to 0.33 loses a percent, which is a barrow on a garage floor, and the mistakes section shows where that lands. If you would rather stay in inches, multiply all three dimensions in inches and divide by 1,728 to get cubic feet, then by 27.
Slab. 20 × 10 ft at 4 in: 20 × 10 × ⅓ = 66.67 cu ft ÷ 27 = 2.47 cu yd. Footing. A 120 ft run of footing 16 in wide and 8 in deep: 120 × 1.333 × 0.667 = 106.67 cu ft ÷ 27 = 3.95 cu yd. Round pier. A 12 in tube 3 ft deep: π × 0.5² × 3 = 2.36 cu ft ÷ 27 = 0.09 cu yd, which the tool prints as 0.1 cu yd once the waste is on. Then the order: multiply by 1.1 for the 10 percent waste and round up to the next quarter yard, so 2.47 becomes 2.72 and the order is 2.75; 3.95 becomes 4.35 and the order is 4.5. Divide the order by the truck size and round up for the loads.
A metric plant wants cubic metres: divide cubic feet by 35.315, or cubic yards by 1.308; one cubic yard is 0.7646 m³ and the tool prints the metric row under the yards. For an L-shaped patio, a slab with a thickened edge, three areas added together, or a contractor's number you want to check line by line, how to calculate concrete yards walks the method shape by shape.
Square feet to cubic yards of concrete, and yards back to square feet
At 4 in a cubic yard covers exactly 81 sq ft, because 27 ÷ ⅓ = 81, so square feet ÷ 81 is the trade shortcut for a 4 in slab and nothing else: at 5 in the divisor is 64.8 and at 6 in it is 54. Each extra inch on 100 sq ft is 0.31 cubic yards, which is why a slab poured at 6 in takes half again as much concrete as the same footprint at 4. The first table runs the common footprints through the formula at the three thicknesses people actually pour, then shows what the tool would put on the order line with its 10 percent waste and quarter-yard rounding.
| Area | 4 in | Order | 5 in | Order | 6 in | Order |
|---|---|---|---|---|---|---|
| 100 sq ft | 1.23 | 1.5 | 1.54 | 1.75 | 1.85 | 2.25 |
| 144 sq ft | 1.78 | 2 | 2.22 | 2.5 | 2.67 | 3 |
| 200 sq ft | 2.47 | 2.75 | 3.09 | 3.5 | 3.7 | 4.25 |
| 300 sq ft | 3.7 | 4.25 | 4.63 | 5.25 | 5.56 | 6.25 |
| 400 sq ft | 4.94 | 5.5 | 6.17 | 7 | 7.41 | 8.25 |
| 500 sq ft | 6.17 | 7 | 7.72 | 8.5 | 9.26 | 10.25 |
| 600 sq ft | 7.41 | 8.25 | 9.26 | 10.25 | 11.11 | 12.25 |
| 800 sq ft | 9.88 | 11 | 12.35 | 13.75 | 14.81 | 16.5 |
| 1,000 sq ft | 12.35 | 13.75 | 15.43 | 17 | 18.52 | 20.5 |
| 1,200 sq ft | 14.81 | 16.5 | 18.52 | 20.5 | 22.22 | 24.5 |
| 1,500 sq ft | 18.52 | 20.5 | 23.15 | 25.5 | 27.78 | 30.75 |
| 2,000 sq ft | 24.69 | 27.25 | 30.86 | 34 | 37.04 | 40.75 |
The second table is the reverse, for the number on a truck ticket or a bid: what the yards will cover at a given thickness. Ten yards is 810 sq ft at 4 in and 540 sq ft at 6 in, before waste, which is the check to run when a contractor quotes yards for a slab you know the size of. Coverage by every thickness from 3 to 12 in, with the bag count and the slab weight per square foot, is on the concrete slab calculator.
| Yards on the ticket | At 4 in | At 5 in | At 6 in |
|---|---|---|---|
| 1 cu yd | 81 | 64.8 | 54 |
| 2 cu yd | 162 | 129.6 | 108 |
| 3 cu yd | 243 | 194.4 | 162 |
| 5 cu yd | 405 | 324 | 270 |
| 8 cu yd | 648 | 518.4 | 432 |
| 10 cu yd | 810 | 648 | 540 |
| 12 cu yd | 972 | 777.6 | 648 |
Ordering ready-mix: quarter-yard steps, minimum loads, short loads and truck loads
Ready-mix is batched and ticketed in fractions of a yard, quarters at most plants, which is why the tool prints an order line separately from the volume. The volume with waste for the default slab is 2.72 cubic yards; the plant cannot batch that, so the order is the next quarter up, 2.75. A 10 × 10 pad is 1.36 and orders as 1.5; a 24 × 24 garage floor is 7.82 and orders as 8, which fills an 8-yard truck exactly. The tool never rounds down: the difference between 2.72 and 2.75 is a wheelbarrow, and the difference between 2.75 and 2.5 is a cold joint across the slab while a second truck is found.
Truck loads are the order divided by the loaded capacity of the truck, rounded up. A standard rear-discharge mixer carries about 8 to 11 cubic yards on the road, with 10 the common figure, even though the drum is rated for more; the limit is the axle weight on the road, and a plant will short-load a heavy mix, a long chute or a soft driveway. One rural slab in the forum threads read for this page was delivered at 7 yards a load to protect a 600 ft drive. Set the truck size to what your plant tells you and the count changes with it: a 16.5-yard order is 2 loads on a 10-yard truck and 3 on an 8.
| Order | 8 cu yd truck | 9 cu yd | 10 cu yd | 11 cu yd |
|---|---|---|---|---|
| 3 cu yd | 1 | 1 | 1 | 1 |
| 5 cu yd | 1 | 1 | 1 | 1 |
| 8 cu yd | 1 | 1 | 1 | 1 |
| 9 cu yd | 2 | 1 | 1 | 1 |
| 10 cu yd | 2 | 2 | 1 | 1 |
| 11 cu yd | 2 | 2 | 2 | 1 |
| 12 cu yd | 2 | 2 | 2 | 2 |
| 15 cu yd | 2 | 2 | 2 | 2 |
| 18 cu yd | 3 | 2 | 2 | 2 |
| 20 cu yd | 3 | 3 | 2 | 2 |
| 25 cu yd | 4 | 3 | 3 | 3 |
| 30 cu yd | 4 | 4 | 3 | 3 |
The small end has its own rules. A plant sets a minimum load, and below a second, higher threshold it adds a short-load charge for the capacity the truck carried empty; both are policy, not code, and both vary by plant and season. The tool prompts at 1 yard, where many plants will not deliver at all, and at 3 yards, where a surcharge is usual, but those are prompts to ask, not the answer. Under the minimum the job is bags or a towable mixer, which is where the bags of concrete calculator takes over; the volume and labour break-even between the two is worked in bagged concrete vs ready-mix. This site prints quantities only; nothing on this page is a quote.
Six things to ask the plant before you book
| Ask | Why it matters |
|---|---|
| Minimum load | The smallest order they will send a truck for; 1 to 5 yards is the range seen, and some plants refuse anything under a yard |
| Short-load threshold | The order size below which a surcharge applies; often well above the minimum, and the tool's 3-yard prompt is a placeholder for the real number |
| Batch step | Whether they batch in quarter yards, halves or whole yards; the order line here assumes quarters |
| Truck size | The loaded capacity they will actually send to your address, not the drum rating; long or soft driveways get lighter loads |
| Unload time | Minutes allowed per yard before standby applies; one invoice seen read 5 minutes per yard, so a 10-yard truck is about 50 minutes |
| Truck spacing | How far apart consecutive trucks arrive, so the second load reaches the form before the first has stiffened |
Two more numbers decide how a multi-truck pour is laid out. Concrete is normally placed within about 90 minutes of batching, or 300 drum revolutions, the limit suppliers commonly work to under the ready-mix standard ASTM C94 unless the purchaser allows more; hot weather shortens it. So trucks are spaced, not stacked, and the joint between loads is planned to land on a bulkhead or a control joint, which is the tool's multi-load note, with joint spacing itself on the concrete slab calculator. The other number is the one the tool cannot print: a crew that dumps 21 yards and comes up a yard short waits for a fourth truck with the surface setting, and that seam is a cold joint the width of the slab.
What is a yard of concrete? 27 cubic feet, 81 square feet, 0.76 cubic metres
A yard of concrete is a cubic yard: 27 cubic feet, the volume of a cube 3 ft on every side. On a ticket, a bid or a phone call, yard and cubic yard mean the same thing, and it is never a square yard, which is 9 sq ft of area with no depth. Spread 4 in thick a yard covers 81 sq ft, a 9 × 9 ft pad or about five sidewalk squares; at 6 in it covers 54. In metric it is 0.7646 m³, so a cubic metre is 1.308 yards. Normal-weight concrete runs about 150 lb per cubic foot, so a yard weighs roughly 4,000 lb, a figure the concrete calculator works through for hauling; and a yard is 45 bags of 80 lb mix, 3,600 lb of dry material, which the bags of concrete calculator counts for every bag size. The how many bags of concrete post lists the jobs that stay under a yard.
Concrete yards for common slabs, footings and piers, with the order and the truck count
The slab table runs the footprints people actually pour at 4 in through the tool: the formula volume, the order line with 10 percent waste rounded to the quarter yard, and the loads on a 10-yard truck. Two pairs are worth reading together. The 24 × 24 garage floor is 7.82 yards with waste and orders as 8, so it fills an 8-yard truck exactly and leaves nothing spare on a 10. A 30 × 40 shop floor at 4 in and a 20 × 40 driveway at 6 in are the same 16.3 yards, because thickness trades against area: the driveway is half the footprint at half again the depth. Thickness by use is the concrete slab calculator; a pier diameter for a deck is the deck footing size calculator.
| Slab | Sq ft | Cu yd | Order | Loads |
|---|---|---|---|---|
| 8 × 8 ft | 64 | 0.79 | 1 | 1 |
| 10 × 10 ft | 100 | 1.23 | 1.5 | 1 |
| 10 × 12 ft | 120 | 1.48 | 1.75 | 1 |
| 12 × 12 ft | 144 | 1.78 | 2 | 1 |
| 12 × 16 ft | 192 | 2.37 | 2.75 | 1 |
| 16 × 20 ft | 320 | 3.95 | 4.5 | 1 |
| 20 × 20 ft | 400 | 4.94 | 5.5 | 1 |
| 20 × 24 ft | 480 | 5.93 | 6.75 | 1 |
| 24 × 24 ft | 576 | 7.11 | 8 | 1 |
| 24 × 30 ft | 720 | 8.89 | 10 | 1 |
| 30 × 30 ft | 900 | 11.11 | 12.25 | 2 |
| 30 × 40 ft | 1,200 | 14.81 | 16.5 | 2 |
Footings and piers are the shapes that fall under the plant minimum. A 40 ft run of 16 × 8 in footing is 1.32 yards by the formula, 1.45 with waste and an order of 1.5, and a single 12 in pier 3 ft deep is 0.1 yards with no truck line at all. Eight of those piers reach 0.77 and order as 1 yard, which is still a short load at most plants. Where the table says no truck line the tool prints the volume without an order row and its loads row reads 1, which is not a delivery; the footing width by soil is on the concrete footing calculator.
| Shape | Cu yd (10 %) | Order | Loads |
|---|---|---|---|
| 40 ft run, 16 × 8 in | 1.45 | 1.5 | 1 |
| 80 ft run, 16 × 8 in | 2.9 | 3 | 1 |
| 120 ft run, 16 × 8 in | 4.35 | 4.5 | 1 |
| 160 ft run, 16 × 8 in | 5.79 | 6 | 1 |
| 1 pier, 12 in × 3 ft | 0.1 | no truck line | — |
| 4 piers, 12 in × 3 ft | 0.38 | no truck line | — |
| 8 piers, 12 in × 3 ft | 0.77 | 1 | 1 |
| 12 piers, 12 in × 3 ft | 1.15 | 1.25 | 1 |
Where the extra yards go: why a pour takes more concrete than the formula
Two garage slabs from the forum threads read for this page tell the same story. One was figured at about 19 yards, ordered at 20 and took 21.5, a 7.5 percent overrun on the order and more on the formula; the other dumped 21 yards and came up a yard short, waiting on a fourth truck with the surface setting. Neither crew had the arithmetic wrong. The formula assumes a subgrade dead flat at the design depth, forms that hold their line, and nothing left in the chute, and no slab gets all three.
The arithmetic behind the gap: a subgrade ½ in low across a 4 in slab is 12.5 percent more concrete, which alone explains the first slab. A driveway or garage graded to fall ¼ in per foot over 24 ft is 6 in deeper at the far edge if the base was left flat, 3 in on average, three quarters again on a 4 in slab; the fix is to grade the base to the same fall, and slope is on the concrete slab calculator. A thickened edge or a turned-down footing is a second shape that was never in the slab formula, and belongs in the footing calculator. A pier hole in soft ground bells out below the tube. Forms bow under 150 lb per cubic foot of wet concrete unless they are staked. And the chute, the barrow, a pump line and the first bucket of a tractor-load pour all hold concrete that never reaches the form; one small slab placed by loader bucket moved a quarter yard a trip against a half-yard bucket.
The 10 percent waste covers the ordinary case: a base that is close, forms that are braced, a short chute. It does not cover a rough subgrade, and the answer to that is a rake and a plate compactor, not 20 percent concrete, with the base itself on the gravel calculator. Order the quarter-yard figure the tool prints, and have a place for the last barrow, a step, an equipment pad, a sidewalk square, rather than a reason to run the corner thin; the full checklist for a slab pour is in concrete for a slab.
Five ways a concrete yardage figure goes wrong
Each of these was found on a published calculator page or a forum answer while researching this page, and each is arithmetic rather than judgement. The first is the most expensive in both directions: a page that tells you to round to the nearest whole yard because you cannot order a fraction is wrong on the fact, since plants batch in quarters, and wrong on the outcome, since 1.36 rounded to 1 leaves a 10 × 10 pad a third of a yard short. The second is the classic: a 10 × 8 ft patio at 4 in written up as 10 × 8 × 4 = 320 cubic feet, then divided by 27 to give 11.85 yards, twelve times the real 0.99, because the 4 was never divided by 12.
- Whole-yard rounding. The order line rounds up to the quarter, never to the yard and never down.
- Inches not converted. Thickness goes in as feet, or all three dimensions go in as inches and the product is divided by 1,728.
- Decimal shortcuts. 0.33 for 4 in and 0.416 for 5 in each lose about 1 percent; on a 24 × 24 garage that is 7.04 against 7.11, a barrow light, and on an 80 × 24 driveway 29.58 against 29.63.
- Square yards. Dividing square feet by 9 gives square yards, a flooring unit with no depth; concrete is cubic.
- Bag arithmetic from memory. A yard is 45 bags of 80 lb, not 34; every bag figure belongs on the bags of concrete calculator.
| Mistake | Wrong | Right |
|---|---|---|
| Rounding to the whole yard | 2.72 → 3 (a quarter yard wasted); 1.36 → 1 (a third of a yard short) | 2.75 and 1.5, the next quarter up |
| Thickness left in inches | 10 × 8 × 4 = 320 cu ft = 11.85 cu yd | 10 × 8 × ⅓ = 26.67 cu ft = 0.99 cu yd |
| 0.33 and 0.416 for 4 in and 5 in | 24 × 24 × 0.33 ÷ 27 = 7.04; 80 × 24 × 0.416 ÷ 27 = 29.58 | 7.11 and 29.63 with ⅓ and 5⁄12 |
| Square feet ÷ 9 | 200 sq ft ÷ 9 = 22.22 (square yards) | 200 × ⅓ ÷ 27 = 2.47 cu yd at 4 in |
| Bags per yard from memory | 34 bags of 80 lb | 45 (27 ÷ 0.60), on the bags calculator |
The two code figures the calculator checks: IRC 2021 R506.1 and R403.1.1
Floors shall be a minimum 3-1/2 inches (89 mm) thick (for expansive soils, see Section R403.1.8). That is the slab warning, from R506.1 on page 5-28 of the Chapter 5 PDF of the 2021 Seattle Residential Code, which reprints the IRC text on that page without local amendment. It governs a slab that is the floor of a house, a basement or a garage, and says nothing about a patio or a walk, which is why the tool prints the yards for a thin slab and only warns.
The minimum width, W, and thickness, T, for concrete footings shall be in accordance with Tables R403.1(1) through R403.1(3) and Figure R403.1(1) or R403.1.3, as applicable, but not less than 12 inches (305 mm) in width and 6 inches (152 mm) in depth. That is the footing warning, R403.1.1 on page 4-3 of the Chapter 4 PDF; the tool checks the 6 in depth and leaves the width to you, since the width comes from the soil in Table R403.1 and is worked on the concrete footing calculator, with frost depth under R403.1.4 and the full text in concrete footing and slab code. Truck capacity, batch steps, minimum loads and discharge times are not in the code at all; they are plant practice and an industry standard, and the page says so where it uses them.
Which concrete calculator do you need?
Every concrete tool on this site starts from the same volume; each one adds the input its job turns on. Use this page when the question is what to tell the plant; move across when the question is the shape, the thickness, the bags, the footing or the post.
| Job | Use | What it adds |
|---|---|---|
| Truck order, loads, short loads | This page | Quarter-yard rounding, truck loads, plant thresholds, square feet to yards |
| Mixed shapes, steps, curb, bags | Concrete calculator | Cubic yards for eight shapes, bag counts, weight per yard |
| Slab thickness, base, joints | Concrete slab calculator | Thickness by use, coverage by thickness, joint spacing, slope |
| Bag count for a small pour | Bags of concrete calculator | 80, 60, 50 and 40 lb bags with waste, bags per yard, pallets |
| Footing under a wall or pier | Concrete footing calculator | Width by soil from Table R403.1, frost depth, trench volume |
| Post in the hole | Post hole concrete calculator | Subtracts the post from the hole; bags per hole |
| Stone under the slab | Gravel calculator | Base volume in tons, compaction |
| Rebar or mesh count | Rebar calculator | Bar count for a slab grid |
| Pier diameter for a deck | Deck footing size calculator | Footing size from load and soil bearing |
| Driveway, patio, sidewalk, shed pad | Driveway, patio, sidewalk, shed base | Thickness by use, fall, panel layout |
| All of them | Concrete calculators hub | Every concrete tool on the site in one place |
Concrete yards questions from job sites and forums
How many yards of concrete do I need for a 10 x 10 slab?
About 1¼ cubic yards at 4 in, and an order of 1½. The formula is 10 × 10 × ⅓ = 33.33 cubic feet, ÷ 27 = 1.23 cubic yards; with the tool's 10 percent waste that is 1.36, and the plant batches in quarter yards, so the order line reads 1.5. At 5 in the same pad is 1.54 yards and at 6 in 1.85. Either order is under most plants' short-load threshold, so the bags calculator is the other route: 62 bags of 80 lb at 4 in.
How do I calculate concrete yards?
Length × width × thickness, all in feet, divided by 27, then add waste and round up to the quarter yard. The step-by-step method for odd shapes, added areas and checking a bid is in how to calculate concrete yards.
How many cubic feet are in a cubic yard?
Twenty-seven. A yard is 3 ft, so a cubic yard is 3 × 3 × 3 = 27 cubic feet, and every yardage formula ends by dividing cubic feet by 27. The reverse is also useful: one cubic foot is 0.037 cubic yards, and a 12 in sonotube 3 ft deep at 2.36 cubic feet is 0.09 yards. In metric a cubic yard is 0.7646 cubic metres, or 27 × 0.0283, which is the third row the calculator prints.
How many yards of concrete are in a concrete truck?
Usually 8 to 11 cubic yards loaded, with 10 the common figure for a standard rear-discharge mixer. The drum is rated for more, but the load is limited by axle weight on the road, so a plant will send less for a heavy mix, a long chute or a soft driveway; one rural pour was delivered at 7 yards a load to protect the drive. Ask the plant what size they will send to your address and set the tool's truck capacity to match; the loads row divides the order by that figure and rounds up.
Why does the calculator round my order up to the quarter yard?
Because plants batch and ticket in quarter-yard steps, and the tool never rounds down. The default slab is 2.72 cubic yards with waste; the plant cannot load 2.72, so the order is the next quarter up, 2.75. Rounding to the nearest whole yard, which some pages advise, wastes a quarter yard at the top end and leaves a 10 × 10 pad a third of a yard short at the bottom. The quarter above is a wheelbarrow of concrete; the quarter below is a cold joint and a second truck.
What is a short load of concrete?
An order below the plant's minimum, or below the threshold at which it adds a charge for the truck capacity that rode empty. Both figures are plant policy and vary: minimums of 1 to 5 yards are seen, and a surcharge zone up to about 3 yards or more is usual. The calculator prompts at 1 yard and at 3 yards as reminders to ask, not as the plant's numbers. Below the minimum the job is bags or a towable mixer, and the bags of concrete calculator counts them; this site prints quantities only, never a quote.
How many square feet does a yard of concrete cover?
Eighty-one square feet at 4 in thick, 64.8 at 5 in and 54 at 6 in, before waste. The figure is 27 cubic feet divided by the thickness in feet, so at 3 in it is 108 and at 8 in it is 40.5. A 9 × 9 pad is one yard at 4 in, and ten yards on a ticket cover 810 sq ft at 4 in or 540 at 6 in. The full coverage table by thickness, with bags and slab weight, is on the concrete slab calculator; the square-feet tables above run both directions.
How many yards of concrete for a 24 x 24 garage slab?
7.11 cubic yards at 4 in by the formula, 7.82 with 10 percent waste, and an order of 8, which fills an 8-yard truck exactly or rides on a 10 with two yards to spare. At 6 in the same floor is 10.67 yards, 11.73 with waste, an order of 11.75 and two loads on a 10-yard truck. A garage floor is a floor under R506.1, so 3½ in is the code minimum and 4 in the usual pour; the thickness by use is on the concrete slab calculator.
Does the waste allowance go on before or after rounding?
Before, and once. The tool multiplies the formula volume by 1.1, then rounds that figure up to the next quarter yard, then divides the rounded order by the truck size: 2.47 × 1.1 = 2.72, up to 2.75, one load. Adding 10 percent again on the phone doubles the margin; rounding first and then adding waste can push the order across a truck boundary for nothing. If a plan or a bid already carries a margin, set the waste to 0 and let the rounding do the rest.
Why did my pour take more concrete than the calculator said?
Almost always the subgrade. Half an inch low across a 4 in slab is 12.5 percent more concrete, and a base left flat under a slab graded to fall ¼ in per foot averages 3 in deeper over 24 ft. Forms that bow, a thickened edge that was never in the slab arithmetic, a pier hole that bells out in soft ground, and what stays in the chute and the barrow all add on top. The 10 percent waste covers the ordinary case; a rough base needs grading, not 20 percent concrete.
How much does a yard of concrete weigh?
Roughly 4,000 lb for normal-weight concrete, about 150 lb per cubic foot times 27. The concrete calculator works that figure through for hauling and trailer loads.
How many bags of concrete make a yard?
Forty-five bags of 80 lb, 60 of 60 lb, 72 of 50 lb or 90 of 40 lb, all from 27 divided by the yield on the bag. Every bag count is on the bags of concrete calculator.
How long can concrete stay in the truck before it is poured?
About 90 minutes from batching, or 300 drum revolutions, whichever comes first, is the limit suppliers commonly work to under the ready-mix standard ASTM C94 unless the purchaser allows otherwise; hot weather shortens it and a retarder can extend it. It is a standard and a plant rule, not building code. It is why trucks on a multi-load pour are spaced rather than stacked, and why the seam between loads is planned to land on a bulkhead or a control joint rather than wherever the first truck ran out.
How many yards of concrete for a 12 in sonotube 3 ft deep?
0.09 cubic yards by the formula, 0.1 with waste: π × 0.5² × 3 = 2.36 cubic feet, ÷ 27. The tool prints no order line for it, because nothing under half a yard goes on a truck; it is 5 bags of 80 lb on the bags calculator. Eight of those tubes reach 0.77 yards with waste and order as 1 yard, twelve reach 1.15 and order as 1.25, still a short load at most plants. Nothing is subtracted for a post; the post hole calculator does that.
Is a yard of concrete the same as a square yard?
No. A yard of concrete is a cubic yard, 27 cubic feet of volume; a square yard is 9 square feet of area with no depth, the unit flooring and turf are sold in. Dividing a slab's square footage by 9 gives square yards, which is why that shortcut lands a 200 sq ft patio at 22 rather than 2.47. Concrete always needs the thickness: square feet × thickness in feet ÷ 27, or square feet ÷ 81 for a 4 in slab.
How many yards of concrete fit in a 20 x 40 driveway at 6 in?
14.81 cubic yards by the formula, 16.3 with 10 percent waste, an order of 16.5 and two loads on a 10-yard truck, three on an 8. That is the same concrete as a 30 × 40 shop floor at 4 in, because thickness trades against area. The second truck should arrive before the first load stiffens, and the seam between them should land on a control joint across the drive; slope, base and joint spacing for a driveway are on the concrete slab calculator.
Source and verification of these yardage figures
Every cubic-yard figure on this page is length × width × thickness ÷ 27, or π r² × depth ÷ 27, regenerated from the same formula the calculator runs, with the order rounded to the quarter yard and the loads divided by the truck size exactly as the tool does, and checked by script against the copy before publishing; if a number here disagrees with the tool, the tool is right and the page has a typo. The two code sentences are IRC 2021 R506.1, page 5-28 of the Chapter 5 PDF, and R403.1.1, page 4-3 of the Chapter 4 PDF of the 2021 Seattle Residential Code; neither carries a local amendment in the line used. Truck capacities, batch steps, minimum loads, short-load thresholds and unload allowances are trade practice reported by plants and crews and are labelled as such; the discharge window is the ready-mix standard as commonly specified. Pour reports are paraphrased from public forum threads with no names. How every figure on this site is checked is on the methodology page; who builds it is on the about page.