Ready-Mix or Bags? Which Is Cheaper?
The crossover is around one cubic yard. Here is the arithmetic behind it.
Above roughly one cubic yard, ready-mix is cheaper. Below it, bags win — not because bags are efficient, but because almost every supplier bills for a minimum of one yard. A 20×20 slab costs about $896 as ready-mix against $1,470 in bags; 20 fence posts cost $120 in bags against a $165 minimum delivery.
Estimates only. Textured walls, high ceilings, sprayers and major colour changes can all increase the amount you need. Always buy slightly more than the calculation suggests.
The crossover, job by job
| Pour | Volume | Cubic yards | Bags | Cheaper |
|---|---|---|---|---|
| 20 fence posts at 8" x 24" | 11.6 cu ft | 0.4 cu yd | 20 × 80 lb | Bags |
| Patio, 10 x 10 at 4" | 36.7 cu ft | 1.4 cu yd | 62 × 80 lb | Ready-mix |
| Patio, 12 x 14 at 4" | 61.6 cu ft | 2.3 cu yd | 103 × 80 lb | Ready-mix |
| Shed base, 10 x 12 at 4" | 44 cu ft | 1.6 cu yd | 74 × 80 lb | Ready-mix |
| Slab, 20 x 20 at 4" | 146.7 cu ft | 5.4 cu yd | 245 × 80 lb | Ready-mix |
| Driveway, 20 x 24 at 5" | 220 cu ft | 8.1 cu yd | 367 × 80 lb | Ready-mix |
At $6 per 80 lb bag and $165 per cubic yard delivered, with a one-yard minimum. The final column is the verdict the calculator reaches.
The minimum order is what decides it
On pure arithmetic, ready-mix wins almost every time. $165 for 27 cubic feet against $6 for 0.6 cubic feet works out at about $6.11 per cubic foot for ready-mix and $10.00 for bags. Ready-mix is 40 % cheaper by volume.
What breaks the comparison is that you cannot buy 0.4 yards of ready-mix. Suppliers bill a minimum — usually one cubic yard, sometimes with an additional short-load fee on top. Order half a yard and you pay for a yard.
So the real comparison is:
- Bags: number of bags × price, no minimum, no delivery.
- Ready-mix: the larger of your actual volume and one cubic yard, times the price, plus any short-load fee.
That is the calculation this site does for you, and it is the reason 20 fence posts come out cheaper in bags.
Price is not the only factor
Three things outweigh a small price difference, and all three favour ready-mix.
- Speed and continuity. Concrete sets in about an hour after mixing. A truck places the whole pour in one continuous operation. Bags are mixed a few at a time, and on anything large that means cold joints between batches — permanent weak seams.
- Labour. 45 bags is 3,600 lb of material to load, carry, open, mix and place. That is most of a day of hard work. The truck is done in twenty minutes.
- Consistency. Ready-mix arrives at the correct slump and water-cement ratio. Bagged mix depends on how much water you add, and adding too much water to make it easier to work is the single most common cause of weak, dusty, cracking concrete.
There is one factor that favours bags, and it is decisive when it applies: access. If a truck cannot get within chute reach, bags are the only option and the extra cost is simply the price of the site.
How to decide in ten seconds
- Work out the volume with the calculator above.
- Is it under one cubic yard? Bags, unless access is easy and you want the speed.
- Is it over two cubic yards? Ready-mix. The labour alone settles it.
- Between one and two yards? This is genuinely close. Price it both ways, then ask whether you would rather spend $100 or a day of your life.
- Can a truck reach? If not, bags — regardless of the arithmetic.
Frequently asked questions
Is it cheaper to mix your own concrete?
Only under about one cubic yard, and only because ready-mix suppliers bill a one-yard minimum. Above that, ready-mix is about 40 % cheaper by volume before you count your time.
How many bags of concrete equal a yard?
Forty-five 80 lb bags. At $6 each that is $270, against about $165 for a delivered yard — so ready-mix is cheaper once you need the full yard anyway.
What is a short-load fee?
A surcharge some suppliers add when you order less than a minimum quantity, typically under one to three cubic yards. It exists to cover the cost of sending a truck out with a part load.
Can I mix a yard of concrete by hand?
Technically yes, in about 45 bags, but you cannot place it fast enough to avoid cold joints. For anything approaching a yard, use ready-mix or a mixer and organise help.