There’s a size where mixing bags stops being clever and starts being a bad day. Finding it is mostly arithmetic, and the arithmetic is not close: delivered ready-mix costs roughly half what bagged mix costs per cubic foot, before you count what your Saturday is worth.
The price comparison, per cubic yard
A cubic yard is 27 ft³. Divide that by each bag’s yield to get the bag count, then multiply by the price:
| How you buy it | Yield | Units per yd³ | Unit price | Cost per yd³ | Cost per ft³ |
|---|---|---|---|---|---|
| 40 lb bags | 0.30 ft³ | 90 | ~$4.00 | ~$360 | $13.33 |
| 50 lb bags | 0.375 ft³ | 72 | ~$5.00 | ~$360 | $13.33 |
| 60 lb bags | 0.45 ft³ | 60 | ~$5.50 | ~$330 | $12.22 |
| 80 lb bags | 0.60 ft³ | 45 | ~$6.50 | ~$293 | $10.83 |
| 90 lb bags | 0.675 ft³ | 40 | ~$7.50 | ~$300 | $11.11 |
| Ready-mix, delivered | — | 1 | ~$165 | ~$165 | $6.11 |
Prices are US national-average estimates from mid-2026; ready-mix realistically runs $125–$200+ per cubic yard depending on region, mix design, and fuel surcharges. Confirm both with your local supplier before you commit.
Two things worth noticing. Ready-mix wins on raw material price at every volume — there is no slab size where bagged mix is cheaper per cubic foot. And among bags, bigger is cheaper: 80 lb mix is about 19% cheaper per cubic foot than 40 lb mix. If you’re buying bags and can handle the weight, buy 80s.
So why does anyone buy bags? Because ready-mix has costs that don’t appear in the per-yard price.
What ready-mix actually costs on a small order
- Short-load fee. Trucks dispatch in 0.25 yd³ increments, but suppliers surcharge small loads — typically $50–$150 on anything under about 4 cubic yards. Since almost every residential slab is under 4 yards, assume you’re paying it. The exact threshold varies by supplier, so ask where their line sits before you compare quotes.
- Delivery. Sometimes folded into the yard price, sometimes a separate charge that scales with distance.
- Standby / wait time. You get a free unloading window — commonly a handful of minutes per yard — and pay by the minute after it. A truck idling while you figure out your screed board is expensive.
- Access. A loaded mixer weighs a lot and the chute reaches maybe 15–18 feet from the truck. A backyard slab means wheelbarrowing anyway, or paying for a pump. Trucks also crack driveways and rut lawns.
- A hard deadline. The truck arrives when it arrives, with roughly an hour of working time on board. Forms, base, mesh, tools, and helpers all have to be ready before it turns up. Bags wait patiently; a truck does not.
What bags actually cost in labor
The material premium is the small half of it. Take a 12 × 12 slab at 4 inches — 48 ft³, or 88 bags of 80 lb mix with 10% waste:
- That’s 7,040 lb of dry mix to load, unload, and lift onto a mixer, plus roughly 66 gallons of water to add.
- A wheelbarrow takes about two bags at a time. That’s 44 barrow loads.
- Standard mix gives you about an hour of working time, and that clock starts with the first batch, not the last.
That last point is the one that bites. One person mixing 88 bags cannot place them inside a single working window — the first section will be setting hard while you’re still mixing the last. The result is a cold joint: an unbonded plane through the slab where the two pours meet, and a crack that will find it.
Rough capacity, assuming a rented mixer and people who aren’t stopping for lunch:
| Bags (80 lb) | Volume | Realistic crew | Verdict |
|---|---|---|---|
| Up to ~15 | ~0.33 yd³ | 1 person | Bags, comfortably |
| ~15–25 | ~0.5 yd³ | 2 people | Bags, work fast |
| ~25–45 | ~0.5–1 yd³ | 3 people + mixer | Either — price both |
| 45+ | 1 yd³+ | 4+ people, or don’t | Ready-mix |
The crossover, by slab size
This is the comparison that matters, because it puts the short-load fee where it belongs — inside the ready-mix number, not in a footnote:
| Slab (4″) | Volume | 80 lb bags | Bag cost | Ready-mix | Mix + short-load | Buy |
|---|---|---|---|---|---|---|
| 4 × 4 | 5.3 ft³ (0.20 yd³) | 10 | ~$65 | 0.25 yd³ · $41 | $91–191 | Bags |
| 8 × 8 | 21.3 ft³ (0.79 yd³) | 40 | ~$260 | 1.00 yd³ · $165 | $215–315 | Toss-up |
| 10 × 10 | 33.3 ft³ (1.23 yd³) | 62 | ~$403 | 1.50 yd³ · $248 | $298–398 | Ready-mix |
| 12 × 12 | 48.0 ft³ (1.78 yd³) | 88 | ~$572 | 2.00 yd³ · $330 | $380–480 | Ready-mix |
| 16 × 20 | 106.7 ft³ (3.95 yd³) | 196 | ~$1,274 | 4.50 yd³ · $743 | $743 (no fee) | Ready-mix |
| 20 × 20 | 133.3 ft³ (4.94 yd³) | 245 | ~$1,593 | 5.50 yd³ · $908 | $908 (no fee) | Ready-mix |
Read the pattern rather than the individual rows. Below about half a cubic yard — call it 25 bags of 80 lb mix — the surcharge is a large fraction of the order and bags win outright. Around 0.75 to 1 yard the two land on top of each other, and the tiebreaker is access, timing, and how many people you have. From about 1.25 yards up, ready-mix wins even in the worst case, and the gap only widens: at 4 yards the fee disappears entirely and bags cost roughly 70% more than the truck.
That’s the crossover the concrete calculator uses: at or above about a cubic yard, order the truck. Anything much past that isn’t a close call.
The options in the middle
Bags and a mixer truck aren’t the only two choices, and the middle range is exactly where the alternatives shine:
- Volumetric (mix-on-site) trucks carry sand, stone, cement, and water separately and mix to order at the curb. You pay for what you actually use, there’s no hour-long clock on unmixed material, and small loads don’t carry the same penalty. Often the best answer for 1–3 yards.
- Trailer-mount / U-cart — you tow 1–2 yards of wet mix home from the yard. Cheap, but you need a capable tow vehicle and the clock is running the moment it’s loaded.
- Short-load trailers delivered by the supplier, same idea without your truck.
- Renting a 6–9 ft³ electric mixer instead of hand-mixing. It roughly triples a small crew’s throughput and is the difference between 40 bags being possible and being miserable.
Things that decide it for you
Sometimes volume isn’t the deciding factor:
- No truck access. A courtyard, a backyard behind a gate, or a steep drive can rule out ready-mix regardless of size — or add a concrete pump to the bill.
- A pour you must do in stages. Post holes, footings, and small pads poured on different days are a bag job by definition.
- Fast-setting mix for posts. For fence and mailbox posts, fast-setting bags poured dry into the hole are the right tool. Note that specialty mixes have different yields than standard mix — don’t reuse the 0.60 ft³ figure, read the bag.
- Storage and returns. Unopened bags go back to the store; leftover ready-mix is your problem, and cement dust in a damp garage turns to rock in a season.
- You want it finished properly. A truck plus a hired finisher is a very different result from 88 bags and a rented float. Compare against DIY vs hiring a pro before assuming DIY saves money — a pro-installed basic 4-inch slab runs about $4–$8 per sq ft all in.
Frequently asked questions
Is ready-mix cheaper than bags? Per cubic yard, yes, always — about $165 delivered against $293 in 80 lb bags. Bags only win below roughly half a yard, once short-load fees and delivery minimums are counted.
How many bags of concrete equal a yard of ready-mix? 45 bags of 80 lb, 60 of 60 lb, or 90 of 40 lb. That’s 3,600 lb of dry mix in the 80 lb case.
What’s the minimum ready-mix order? Trucks dispatch in 0.25 yd³ increments, so there’s rarely a hard minimum — but most suppliers add a $50–$150 short-load fee below about 4 cubic yards. That fee, not the yard price, is what decides small pours. Ask for it as a line item when you get the quote.
Can I mix bags and ready-mix on the same pour? Don’t plan on it. Different batches placed at different times bond poorly, and you’ll be improvising a joint while the concrete sets. Order enough of one thing, with 10% waste on top.
How much does a truck hold? A standard mixer carries roughly 10 cubic yards, so a residential slab is a part load either way — which is exactly why the fee structure on small orders matters more than the per-yard price.
The short answer
Run your volume through the concrete calculator. Under ½ cubic yard (about 25 × 80 lb bags), buy bags. Over 1 cubic yard, order ready-mix — it’s roughly half the material cost and a fraction of the work. In between, get a quote including the short-load fee, and look at a volumetric truck before you commit to hauling 40 bags.
More on sizing the pour in how much concrete do I need and how thick the slab should be.