Bags are simpler under about 1 cubic yard (45 bags of 80 lb). Above 1 cubic yard, ready-mix is usually cheaper: about $160 to $195 a yard before fees, versus about $270 in bags.
The quick rule
- Under about 1 cubic yard: bags are usually simpler. You avoid truck minimums and fees.
- Over about 1 cubic yard: ready-mix is usually cheaper per yard and saves hours of heavy mixing.
- Over 2 cubic yards: ready-mix almost always wins on both cost and labor.
Why: the cost per cubic yard
One 80 lb bag yields about 0.60 cubic feet of concrete, so it takes 45 bags to make one cubic yard (27 cubic feet). At about $6 per bag, that is roughly $270 per cubic yard in material. (SlashGear (opens in a new tab))
Ready-mix costs about $160 to $195 per cubic yard delivered as a full load. (Concrete Network (opens in a new tab)) Small orders often add delivery and short-load fees, which is why bags can still win on tiny jobs.
Worked example: a 10 x 10 slab at 4 inches
- 10 x 10 x 0.333 ft = 33.3 cubic feet = 1.23 cubic yards
- Bags: 33.3 / 0.60 = 55.6, so 56 bags of 80 lb, about $336 at $6 each
- Ready-mix: 1.23 x $160 to $195 = about $198 to $241, plus any delivery and short-load fees
- Weight to handle with bags: 56 x 80 lb = about 4,480 lb
For this slab, ready-mix is likely cheaper even after a modest fee, and it saves you mixing 56 bags by hand.
Things to ask the ready-mix plant
- What is your minimum order, and what is the short-load fee for my amount?
- Is delivery included in the price per yard?
- How long can the truck wait while you place and finish the concrete?
- Can the truck reach my pour site, or will I need a pump or wheelbarrows?
When bags still make sense
- Fence posts, deck footings and small pads under about half a yard.
- Jobs the truck cannot reach.
- Pours you need to do in stages over several days.
Run your exact size through the concrete calculator to get cubic yards and bag counts, then get one ready-mix quote for the same amount.