The numbers first, because they settle most of the argument.
| Bag | Yield | Bags per cubic yard |
|---|---|---|
| 40 lb | 0.30 cu ft | 90 |
| 60 lb | 0.45 cu ft | 60 |
| 80 lb | 0.60 cu ft | 45 |
A cubic yard is 27 cubic feet. A 10 × 10 patio at 4 inches thick is 1.23 cubic yards — 55 bags of 80 lb, which is two and a quarter tons of material to buy, move, and mix.
The real constraint is time, not money
Mixed concrete has to be placed, consolidated and finished before it stiffens. Working from bags, a two-person crew mixes and places somewhere around 8 to 12 bags an hour with a mixer, far fewer with a wheelbarrow and a hoe.
Fifty-five bags is therefore five hours or more of continuous work, and the first batch is well into its set before the last one is poured.
That creates a cold joint — a plane inside the slab where fresh concrete met concrete that had already begun to set. It is a permanent weakness and it is where the slab will crack.
For anything that has to be monolithic, this is the argument, and it is not about price.
Where bags genuinely win
- Post holes and small footings. Discrete pours with no continuity requirement, and often mixed dry in the hole.
- Under about half a cubic yard — repairs, a set of steps, a small pad.
- No truck access. A back garden reached through a house is a wheelbarrow job whatever the volume, and then the constraint is placement rather than mixing.
- Working alone over several days, where each pour is a separate element rather than one slab.
Where the truck wins
- Anything over about a yard that must be poured monolithically
- Any driveway or garage slab
- Where finish quality matters, since a consistent factory mix produces a consistent surface that hand batches do not
- Where the specification names a strength. A ready-mix ticket states the mix design and the psi; bags state a nominal strength that depends entirely on how much water went in
The fees that surprise people
Ready-mix pricing has structure beyond the per-yard rate, and it is worth asking about all of it:
Short-load fee. Below a minimum — commonly 3 to 5 yards — there is a surcharge, and it can be substantial on a one-yard order. This is why a small pour sometimes costs nearly as much as a medium one.
Waiting time. The truck allows a set unloading window, often around an hour, and charges by the minute beyond it. Being ready when it arrives is worth real money: forms braced, tools out, crew present, path clear.
Weekend and after-hours rates.
Pumping, where the truck cannot reach the pour. This is a separate contractor and it frequently costs more than the concrete.
Water is where bagged concrete loses strength
A bag's stated strength assumes the water on the label. Adding extra to make it easier to mix and place lowers strength substantially — this is the single largest quality difference between hand-mixed and delivered concrete, and it is invisible until the slab is a year old.
If mixing from bags, measure the water rather than judging it, and mix stiffer than feels comfortable.
A practical rule
Under half a yard, buy bags. Over one and a half yards in a single monolithic pour, order a truck and accept the short-load fee. In between, the deciding question is whether the pour has to be continuous — and if it does, the truck is the answer even when the bags are cheaper.