How the math works
Volume is length × width × thickness, converted to cubic feet and then cubic yards (27 cubic feet per yard). We add 10% for an uneven base and spillage, then divide by the manufacturer's stated yield per bag:
| Bag | Yield per bag | Bags per cubic yard | 2026 price per bag |
|---|---|---|---|
| 80 lb bags | 0.6 cu ft | 45 | $6 to $8 |
| 60 lb bags | 0.45 cu ft | 60 | $5 to $6.5 |
Bags or a truck
Ready-mix runs $130 to $190 per cubic yard delivered for a standard residential mix. Under about5 yards, most plants add a short-load fee of $50 to $150, and some won't deliver under 1 yard at all. Bagged mix works out to roughly $270 to $360 per yard before your own labor. The calculator above prices both for your slab; the rule of thumb is bags under a yard, truck above it.
One thing the price doesn't show: a yard of bags is 45 bags at 80 lb each, hauled, mixed, and placed before the first batch stiffens. For anything over a few hundred square feet, the truck buys you a slab with no cold joints.
How we get these numbers
Bag yields come from the manufacturers' technical data sheets. Prices come from current published national cost guides and a national retailer's shelf price, checked against each other and refreshed at least twice a year (last: September 2026). Ready-mix prices vary by plant and region; call two suppliers for a real quote. Sources:
- Concrete Network: Concrete Prices 2026, How Much Is a Yard of Concrete?
- Angi: Concrete Cost Per Yard (2026)
- The Home Depot: Quikrete 80 lb Concrete Mix (bag yield and price)
Frequently asked questions
How much concrete do I need for a 10x10 slab?
A 10 × 10 ft slab at 4 inches thick is 33.3 cubic feet, or 1.23 cubic yards of concrete. Order 10% extra for an uneven base and spillage: about 1.36 cubic yards, which is 62 bags of 80 lb mix or 82 bags of 60 lb mix.
How many 80 lb bags of concrete are in a cubic yard?
45. An 80 lb bag yields 0.6 cubic feet of placed concrete (per Quikrete and Sakrete data sheets), and a cubic yard is 27 cubic feet. A 60 lb bag yields 0.45 cubic feet, so a yard takes 60 of those.
Bags or a ready-mix truck: which is cheaper?
Bags cost roughly $270 to $360 per cubic yard at 2026 prices, before your labor. Ready-mix runs $130 to $190 per yard delivered, but most plants add a $50 to $150 short-load fee under about 5 yards. Below roughly one yard, bags usually win on price. Above that, the truck is close on price and far less work: a 10 × 10 slab is 60-plus bags to haul, mix, and place before the first batch sets.
How thick should a concrete slab be?
4 inches for patios, sheds, and walkways. 5 to 6 inches for driveways and garage floors that carry cars. 6 to 8 inches if trucks or heavy equipment will sit on it. Thickness matters more than PSI for a residential slab; check your local code, since some jurisdictions set minimums.
Why order 10% extra?
Subgrade is never perfectly flat, forms bow, and some mix stays in the mixer or wheelbarrow. Running short mid-pour leaves a cold joint you can see forever. Ten percent is the standard margin; go to 15% on a rough or hand-dug base.
Common slab sizes
Precomputed yards, bags, and costs at every thickness, plus what a contractor charges to pour it:
- 10 × 10 slab (a shed base, a small patio, or a hot tub pad)
- 12 × 12 slab (a patio, a larger shed, or a carport pad)
- 16 × 12 slab (a standard backyard patio)
- 20 × 16 slab (a large patio or a workshop floor)
- 20 × 20 slab (a one-car garage floor or a driveway apron)
- 24 × 24 slab (a two-car garage floor)