Concrete
Concrete Bags vs. Ready-Mix: Which Should You Choose?
Bagged concrete or ready-mix truck? Costs per cubic yard, the 1.5-yard break-even rule, quality differences, and a decision matrix for slabs, posts, and driveways.
Standing in your yard picturing the new patio, the classic dilemma appears: haul and mix dozens of 80 lb bags yourself, or book a ready-mix truck? The decision affects your budget, your back, and the quality of the finished slab. Here is the comparison with real numbers.
What each option actually is
Bagged concrete is a pre-blended dry mix of cement, sand, and gravel - add water. Sizes: 40 lb (0.30 ft³ yield), 60 lb (0.45 ft³), 80 lb (0.60 ft³). Shelf life is 6–12 months if kept bone dry.
Ready-mix is batched at a plant to a specified strength (PSI), slump, and admixture package, delivered in a mixer truck holding 7–10 yd³. You can order fiber reinforcement, air entrainment for freeze climates, accelerators for cold weather, or colored mixes.
Cost comparison
| Project | Volume | Bags (80 lb) | Bag cost | Ready-mix cost | Winner |
|---|---|---|---|---|---|
| 4 fence posts | 0.35 yd³ | 16 | $80–110 | N/A (below minimum) | Bags |
| Mailbox/steps repair | 0.2 yd³ | 9 | $45–65 | N/A | Bags |
| 100 ft² pad, 4 in | 1.4 yd³ | 62 | $310–435 | $300–450 w/ short-load fee | Toss-up |
| 15×20 patio, 4 in | 4.1 yd³ | 184 | $920–1,290 + brutal labor | $700–950 | Ready-mix |
| 2-car driveway, 5 in | 8.2 yd³ | 368 | Impractical | $1,300–1,800 | Ready-mix |
Bag prices assume $5–7 per 80 lb bag; ready-mix assumes $150–200/yd³ plus $50–100 delivery and possible short-load fees under 3–4 yards. Prices vary by region and season - get local quotes, then run your own volume through the concrete calculator.
Quality: the water problem
Both products can reach 4,000+ PSI. The difference is control. Plants batch water by weight to a specified water–cement ratio; DIYers batch by eye with a garden hose. Excess water is the classic failure: a soupy, easy-to-move mix can lose a large fraction of its design strength and shrinks more as it dries, which means more cracking. If you use bags: measure water per the bag instructions, mix fully, and resist the urge to loosen the mix beyond specification.
The cold joint problem
Concrete bonds poorly to concrete that has already begun to set. Mixing one bag at a time means each batch partially sets before the next arrives - on a large slab this creates weak seams (cold joints) throughout. This is the strongest argument for ready-mix on any slab bigger than a few wheelbarrow loads: the whole placement happens inside the workable window.
Labor reality check
An 80 lb bag yields 0.6 ft³. A modest 10×10 slab needs 62 bags - that's 5,000 lb of material to load, haul, lift, mix, and place, typically 6–8 hours of hard work for two people with a rented mixer ($60–90/day). The same slab pours from a truck chute in 20 minutes. Price your own labor honestly when comparing.
Decision matrix
| Factor | Choose bags | Choose ready-mix |
|---|---|---|
| Volume | < 1.5 yd³ | ≥ 1.5 yd³ |
| Pacing | Work at your own speed | Crew ready for a 90-minute sprint |
| Access | Narrow gates, backyard | Truck can reach within chute distance (~15 ft) |
| Quality stakes | Posts, repairs, non-structural | Slabs, driveways, anything visible or loaded |
| Weather window | Flexible | Committed date, watch forecast |
When to call a professional
Over about 3 cubic yards, with structural reinforcement, complex drainage slopes, or if you don't own finishing tools (bull float, edger, groover) and haven't finished a slab before - hire a finisher at least for the pour day. Placing and finishing is a perishable skill performed against a clock.
Frequently Asked Questions
How many 80 lb bags make a cubic yard?
45 bags. Each 80 lb bag yields about 0.60 cubic feet, and a cubic yard is 27 cubic feet. At $5-7 per bag that's $225-315 per cubic yard in materials alone, before your labor.
What's the break-even point between bags and ready-mix?
Roughly 1 to 1.5 cubic yards - about a 100-150 sq ft slab at 4 inches. Below that, bags avoid delivery and short-load fees; above it, ready-mix is cheaper, faster, and more consistent.
Is bagged concrete weaker than ready-mix?
Not inherently - bags are rated 4,000+ PSI. But DIYers commonly add too much water, which can cut strength dramatically. Ready-mix is computer-batched to a specified water-cement ratio.
How long do I have to work with ready-mix?
About 60-90 minutes from batching, less in hot weather. Have forms, tools, and helpers completely ready before the truck arrives - trucks also bill standby time by the minute.
Can I pour a slab in sections with bags over several days?
Only if you plan joints deliberately. Each day's stopping point is a cold joint, which is weaker and visible. For structural or vehicle-loaded slabs, pour monolithically - use ready-mix.