Why there is no one answer
Pavement Interactive describes a typical mixing truck as using a 9 to 12 cubic yard drum, and notes that the drum size is limited by the gross vehicle weight of the loaded truck. A drum of that size is not filled to the top. The same source says a drum can be filled to a maximum of 63 percent of its total volume for truck-mixed concrete and 80 percent for central-mixed concrete, citing AASHTO and ASTM C94.
The words “drum size”, “gross volume” and “rated capacity” are not interchangeable, and published sources use them differently. Do not multiply a drum size by a percentage to guess a truck’s load. Use the rating your supplier gives you.
How truck capacity is rated
New Jersey DOT’s truck inspection procedure (MP 38-09) lists what a truck mixer’s plate must show: the manufacturer’s capacity rating, which should not exceed 63 percent of the gross volume of the mixer disregarding the blades, and the capacity of the drum in terms of the volume of mixed concrete. For agitator trucks that carry concrete mixed at a central plant, the same procedure uses 80 percent.
In other words, a truck can have two ratings, one as a mixer and one as an agitator, and the limit that applies depends on whether the concrete is mixed in the truck or at the plant. Producers generally load trucks at or near the rated capacity, according to the Pavement Interactive summary of NRMCA guidance.
- Truck mixer (concrete mixed in the drum): rating at most 63% of gross drum volume.
- Agitator (concrete mixed at a central plant): rating at most 80% of gross drum volume.
- Both ratings are on the truck’s plate; your supplier knows which truck will arrive.
Weight limits the load too
Pavement Interactive notes that the size of a mixing truck’s drum is limited by the gross vehicle weight of the loaded truck. Concrete is heavy: see how much a yard of concrete weighs for typical densities. A truck that could hold more by volume may still be limited by what it may legally carry on the road.
How many truckloads does your pour need?
Divide the quantity you need by the truck’s rated load and round up. Each full truck carries its rated load, and the last truck carries the remainder. The table uses a hypothetical 9 yd³ load only to show the arithmetic. It is not a real truck rating, so replace 9 with the load your supplier quotes.
For example, a 25 yd³ pour with a 9 yd³ load needs 2 full loads and a final load of 7 yd³, which is 3 trucks in total. The last load is the one most likely to be affected by a minimum-load or short-load charge.
| Concrete needed (yd³) | Full loads | Final partial load (yd³) | Trucks in total |
|---|---|---|---|
| 3 | 0 | 3 | 1 |
| 5 | 0 | 5 | 1 |
| 10 | 1 | 1 | 2 |
| 15 | 1 | 6 | 2 |
| 25 | 2 | 7 | 3 |
| 40 | 4 | 4 | 5 |
Short loads and minimum orders
Many suppliers set a minimum load or charge a short-load fee when the order is below a threshold, and the rules vary by supplier and region. Do not assume a number. Ask for it, and enter it into the concrete cost calculator, which keeps the minimum billed quantity and the delivery and short-load charges separate.
Ordering the exact net quantity can leave you short, and a shortfall can mean waiting for a second truck. Decide your allowance from the measured dimensions and site conditions, then confirm the order quantity with the supplier.
Questions to ask the supplier
Before you confirm a delivery, ask:
- What is the rated load of the truck you will send, in cubic yards?
- What is the minimum load, and what is the short-load charge below it?
- How is the order billed: exact quantity, or in fixed increments?
- How long may the truck wait on site, and what happens if the pour runs over?
- Can the truck reach the pour, and is a pump needed?
Sources and further reading
- NJDOT Materials Procedure MP 38-09: Concrete Truck Inspection (effective January 1, 2010) ↗Read directly. Truck mixer capacity rating should not exceed 63 percent of gross drum volume; agitator trucks 80 percent; required plate markings.
- Pavement Interactive: Rigid Pavement Truck Types ↗Read directly, October 12, 2026. Typical mixing drum 9–12 yd³ limited by gross vehicle weight; 63% and 80% fill limits citing AASHTO and ASTM C94; producers load at or near rated capacity.
This article is general quantity-planning information. Confirm product requirements, project specifications, and local rules with the appropriate supplier or qualified professional.