Concrete for a Slab
A standard slab for a shed, patio, or floor is 4 inches thick. Enter your slab dimensions for the cubic yards, bag equivalent, and cost estimate. Bump depth to 5–6 inches for load-bearing slabs.
Source: Ready-mix supplier averages (delivered, short-load fees extra) + Home Depot / Lowe's bag pricing
Estimate concrete for your slab
Prefilled for a 12 × 12 ft slab at 4" — adjust to your size.
Material only, $125–$175 per cubic yard. Delivery and labor not included. Estimates only — not engineering advice.
Tips for slabs
- 4 inches suits patios, shed floors, and walkways; go to 5–6 inches for garages or anything bearing vehicle weight.
- Add a 4-inch compacted gravel base and a vapor barrier under interior slabs.
- Anything over ~1 cubic yard is cheaper as ready-mix delivery than bags.
Concrete cost breakdown
- Ready-mix (per cubic yard)
- $125–$175 per yard delivered. Short loads under ~5 yards often add a $60–$150 small-load fee.
- Bagged concrete
- $5–$8 per 80 lb bag ($0.60 ft³ each) — cheaper only for very small pours; a yard is ~45 bags.
- Finishing / labor (optional)
- $2–$8 per sq ft to form, pour, and finish if you hire a crew.
- Reinforcement & prep
- Rebar/mesh, gravel base, and forms add $1–$3 per sq ft.
Frequently asked questions
How many yards of concrete for a 12x12 slab?
A 12 ft × 12 ft slab at 4 inches is about 1.78 cubic yards, or roughly 1.96 with 10% waste included.
How much concrete do I need for a slab?
Multiply length × width × thickness in feet to get cubic feet, then divide by 27 for cubic yards. A 10 ft × 10 ft slab at 4 inches is about 1.23 cubic yards (≈1.36 with waste). Use the calculator above for your size.
How much does concrete cost per yard?
Ready-mix concrete runs about $125–$175 per cubic yard delivered. Small loads under about 5 yards often carry a short-load fee of $60–$150.
How many 80 lb bags of concrete in a cubic yard?
About 45 bags of 80 lb concrete mix make one cubic yard (each yields roughly 0.6 cubic feet). Bags are cost-effective only for small pours.
How thick should a concrete slab be?
Four inches is standard for patios, sheds, and walkways. Driveways and load-bearing slabs should be 5–6 inches, often with rebar or wire mesh.
How much does a concrete slab cost per square foot?
A plain concrete slab runs about $4–$8 per square foot installed, or roughly $8–$18 with reinforcement, thickening, or a decorative finish. Material-only (ready-mix) is a smaller share — the calculator above shows the concrete cost; labor and prep are extra.