How Many Yards of Concrete Are in a Truck? And the Questions It Gets Confused With

A ready-mix truck holds 8 to 12 cubic yards, or 6.1 to 9.2 cubic meters, according to the National Ready Mixed Concrete Association in its guidance sheet CIP 31, Ordering Ready Mixed Concrete. Most residential deliveries arrive carrying 8 to 10. Concrete weighs 3,780 to 4,050 pounds per cubic yard, and federal regulation 23 CFR 658.17 caps a truck at 80,000 pounds gross with 34,000 pounds on a tandem axle, so weight fills a mixer before volume does. Plan a one-truck pour around 9 cubic yards, and confirm that figure with your dispatcher rather than with the drum rating.

The drum rating and the load on your driveway are two different numbers

I catalogued 2,400 drawer pulls at a Manchester prop house, where a shelf tag named a category and the object on the shelf had dimensions. A tag reading "brass pull, 3 in." meant boss spacing on some and overall width on the rest, and anyone ordering from the tag got the wrong hole pattern often enough that we stopped trusting tags. A mixer's drum rating is a tag.

The McNeilus Bridgemaster spec sheet lists a drum capacity of 11 cubic yards and a 42-inch discharge opening. That is the drum. What the plant loads into it is decided by a scale.

Normalweight concrete has a density of 140 to 150 pounds per cubic foot, per NRMCA's CIP 36. Multiply by the 27 cubic feet in a yard and you get 3,780 to 4,050 pounds per cubic yard. Using the heavier end, and a rear-discharge mixer that scales about 28,000 pounds empty (curb weights typically run 27,000 to 32,000):

| Load | Concrete alone | Gross weight | Headroom to 80,000 lb | |---|---|---|---| | 8 yd³ | 32,400 lb | 60,400 lb | 19,600 lb | | 9 yd³ | 36,450 lb | 64,450 lb | 15,550 lb | | 10 yd³ | 40,500 lb | 68,500 lb | 11,500 lb | | 11 yd³ | 44,550 lb | 72,550 lb | 7,450 lb | | 12 yd³ | 48,600 lb | 76,600 lb | 3,400 lb |

Every load in that table clears 80,000 pounds gross, so why does the plant stop at nine? Gross weight is rarely the binding limit. The same regulation caps a single axle at 20,000 pounds and a tandem at 34,000, and the Federal Bridge Formula tightens those further depending on axle spacing. A three-axle mixer runs out of legal axle capacity long before it runs out of drum. The Bridgemaster carries a load-distribution tag axle for exactly that reason. That axle buys legal payload.

CIP 31 also states plainly that "a loaded concrete truck weighs about 80,000 lbs," which is the figure to give anyone asking whether your driveway can take it.

Turning your forms into yards

The arithmetic is one line. Length in feet, times width in feet, times thickness in feet, divided by 27.

Thickness is where people lose money, because it enters the formula in feet while everyone speaks it in inches. Four inches is 0.333 feet. Five is 0.417. Six is 0.5.

A 24 by 24 slab at four inches gives 576 square feet, times 0.333 equals 192 cubic feet, divided by 27 equals 7.11 cubic yards. A 30 by 30 slab at the same thickness gives 900 square feet, 300 cubic feet, and 11.11 cubic yards.

Now add the cushion. CIP 31 says the quantity ordered "should be 4% to 10% more than an estimate calculated from the plan dimensions to account for contingencies." That turns 7.11 into 7.4 to 7.8, and 11.11 into 11.6 to 12.2.

Round those up. The 24 by 24 slab wants 8 cubic yards and fits a single load with room to spare. The 30 by 30 wants 12, which sits at the top of NRMCA's stated range and against the axle limits above. Six feet in each direction separates a one-truck job from a two-truck job.

Coverage per cubic yard, if you would rather work backward from area:

| Thickness | Sq ft per yd³ | |---|---| | 3.5 in | 92.6 | | 4 in | 81.0 | | 5 in | 64.8 | | 6 in | 54.0 |

Measure the forms rather than the drawing. My mother's sewing box taught me trim names, and it also taught me that the name on the card and the width of the braid inside it drift apart over decades. Subgrade drifts the same way. A quarter inch of over-excavation across 900 square feet is another 0.7 cubic yards you did not plan for, which is most of the reason NRMCA prints a cushion at all.

What to confirm with dispatch before the truck rolls

Ask for the discharge time limit in writing. The common knowledge here went stale five years ago. ASTM C94/C94M-21 removed the 90-minute default. Section 6.1.10 now requires the purchaser to state a time limit when ordering, or the producer to establish one if the purchaser does not, and either way that limit must be printed on the delivery ticket. The 90-minute figure people still quote as a rule traced back to provisions dating from the 1930s. Read your ticket instead, and ask the plant's distance, since travel eats the window.

Beyond that, five things are worth a phone call:

1. The mix designation, which appears on the ticket and confirms the load matches the placement.
2. Slump. CIP 31 makes the producer responsible for the specified slump for 30 minutes after the requested time or after the truck arrives, whichever is later. Thirty minutes, not the whole visit.
3. Air content, if you are in a freeze-thaw region. Delivered tolerance is plus or minus 1.5 percent.
4. Free unloading time. Suppliers commonly allow five to seven minutes per cubic yard, then bill by the minute. A nine-yard load buys roughly 45 to 60 minutes.
5. The short-load fee and where it starts, since most plants charge below three to five yards.

What breaks a one-truck plan

Reach fails before volume does. The McNeilus spec sheet lists a five-foot main chute, a 30-inch transition, and two four-foot extensions, which is 15.5 feet of steel. Usable horizontal reach is shorter, because the chute has to slope for the concrete to run, and swinging the chute hard to one side costs several more feet. Producers commonly quote 12 to 18 feet from the truck. If your far form sits 25 feet from where the truck can stand, the chute never reaches it.

Access is the second failure. Producer delivery terms typically ask for a path at least 10 to 12 feet wide, 14 feet of overhead clearance, and ground firm enough to carry roughly 85,000 pounds. AASHTO's SU-30 design vehicle, the 30-foot single-unit truck that agencies use to model delivery vehicles, sweeps an outside front tire radius of 41.8 feet and a front overhang radius of 43.3 feet. That is a circle roughly 87 feet across.

Crew is the third. At five to seven minutes per cubic yard of placing time, a nine-yard load is close to an hour of continuous work, and the concrete does not pause while you find another wheelbarrow.

The first load is down and the next truck is late

You are watching for a cold joint. ACI's terminology defines a construction joint as the surface where two successive placements meet, including one "occurring as a result of inadvertent delays in concrete placing operations." That is the formal name for what happens when load two arrives after load one has stiffened.

Initial set is the threshold, and the clock only approximates it. ASTM C403 defines initial setting time as the point where sieved mortar reaches 500 psi penetration resistance, and NRMCA's TIP 14 calls three to five hours reasonable for a laboratory mixture. That number moves with temperature. On a sharp bright morning like this one, set runs slower than the same mix would at noon in July, which quietly buys the crew time nobody planned for.

While you wait, do four things. Keep the leading edge alive by covering it rather than letting wind and sun skin it. Leave that edge unfinished, since a bull-floated edge cannot intermingle with the next load. Test the boundary with a vibrator when the truck arrives. If it still penetrates the placed concrete and the two mix, there is no joint. Do not add water beyond the mix design to keep things moving. CIP 31 is explicit that excessive jobsite water addition can delay setting, increase cracking potential, and reduce strength, and that the producer is not responsible for concrete modified at the site.

If the boundary has set, stop treating it as a pour. Clean the surface, remove laitance, and place against it as a joint.

Pump, small truck, or split loads

| Option | Reach | Added cost | Best when | |---|---|---|---| | One large mixer | 12 to 18 ft | None | Under 9 yd³, truck reaches forms | | Two scheduled loads | 12 to 18 ft | Second delivery charge | 10 to 14 yd³, room to swap | | Boom pump | 100 ft plus | $500 to $1,500 | Backyard slabs, gated access | | Smaller truck | Tighter turning circle | Higher per-yard rate | Narrow drives, weight-limited bridges |

My preference for a homeowner slab between 10 and 14 yards is two scheduled loads over one overloaded truck, and it is not close. A split pour costs a delivery fee. An overweight truck refused at the scale costs the day.

The delivery ticket is the record of what is buried

Keep every ticket. Cataloguing taught me that an object without provenance is guesswork forever, and a cured slab hides everything a photograph would need to show.

The ticket carries the mix designation, the batch time, the quantity, the specified time limit for discharge, and any water added at the site. Write on it: where each load went, the outside temperature, where the loads met, and where you moved a form. Sketch the pour on the back with rough dimensions and the location of any joint. Five years on, when a crack appears, that sketch tells a repair contractor whether they are looking at a planned joint, a cold joint, or something structural. Without it, everyone is reading one photograph and calling it a pedigree.

Frequently asked questions

How many yards are in one concrete truck?

Between 8 and 12 cubic yards, per NRMCA's CIP 31, with most residential deliveries carrying 8 to 10. Drums are often rated higher than that, but federal axle and gross weight limits under 23 CFR 658.17 stop the plant from filling them. Ask your dispatcher what they will actually load.

How many yards of concrete do I need for a 24 by 24 slab at 4 inches?

7.11 cubic yards. Multiply 24 by 24 by 0.333 feet, then divide by 27. Add NRMCA's recommended 4 to 10 percent contingency and you land between 7.4 and 7.8, so order 8 cubic yards. That fits comfortably in one truck with weight to spare.

How many yards do I need for a 30 by 30 slab at 4 inches?

11.11 cubic yards before contingency, and 11.6 to 12.2 after adding NRMCA's 4 to 10 percent. Order 12. That sits at the top of the 8 to 12 yard range and above what most plants will legally load, so plan on two scheduled trucks rather than one.

How much does it cost to pour 100 yards of concrete?

The concrete alone runs about $12,000 to $19,500 in 2026, using residential quotes of $120 to $195 per cubic yard. NRMCA's 2023 industry benchmark of $159.68 per cubic yard puts it near $15,970. That is 11 to 13 truckloads. Placement and finishing typically add more than the concrete costs.

What is a concrete truck's capacity in cubic meters?

Roughly 6.1 to 9.2 cubic meters, converting NRMCA's 8 to 12 cubic yard range at 0.7646 cubic meters per cubic yard. CIP 31 itself prints the rounder "5 to 9 m³". A typical 10-yard load is 7.6 cubic meters, and a common 8 m³ mixer abroad is about 10.5 cubic yards.

How many square feet does one yard of concrete cover at 4 inches?

81 square feet, from 27 cubic feet divided by 0.333 feet of thickness. At 3.5 inches it covers 92.6 square feet, at 5 inches 64.8, and at 6 inches 54. Measure your finished subgrade, since an extra quarter inch of depth consumes yards quickly across a large slab.

How far can a mixer truck chute reach?

Usually 12 to 18 feet from the truck. The McNeilus Bridgemaster spec sheet lists a 5-foot main chute, a 30-inch transition, and two 4-foot extensions, totalling 15.5 feet of steel, and usable horizontal reach is less because the chute must slope. Swinging it sideways costs several more feet.