Calculate cubic yards and bag count for slabs, driveways, footings, and walkways.
A 10×10-foot concrete slab at 4 inches thick requires approximately 1.23 cubic yards of concrete — equivalent to about 56 bags of 80 lb ready-mix. Our calculator converts your slab, driveway, footing, or walkway dimensions directly to cubic yards and bags, and includes rebar, wire mesh, forms, and gravel base quantities.
Concrete is unforgiving: you can't add more once it's mixed, and you can't use partial yards from a ready-mix truck. Ordering too little means a cold joint — a weak seam where the first pour hardened before the second was placed. Ordering too much wastes $150–$200 per cubic yard. Calculating precisely before you order is one of the most important steps in any concrete project.
Ready-mix (delivered by truck) is the right choice for any project larger than 1 cubic yard. For a 10×10 slab at 4 inches, a ready-mix truck delivers the entire pour in one consistent batch — eliminating cold joints and the exhausting work of mixing 56+ bags by hand. For small projects like fence posts, step repairs, or small footings under 1 cubic yard, 60 lb or 80 lb bags are practical and economical. Our calculator shows both options so you can choose based on project size and budget.
Thickness depends on the application and expected load. Residential sidewalks: 4 inches. Residential driveways: 4–6 inches (6 inches where heavy trucks access). Structural slabs and garage floors: 4–6 inches over a compacted gravel base. Footings: typically 8–12 inches deep, 16–24 inches wide — check local code, as footing size is governed by frost depth and soil bearing capacity. Steps and curbs: 6–8 inches. When in doubt, pour thicker — adding 1 inch to a 10×10 slab costs approximately $90 more in concrete but dramatically increases structural capacity and reduces cracking.
Rebar and wire mesh both add tensile strength to concrete, which is strong in compression but weak in tension. Rebar is used for structural applications: footings, walls, thicker slabs, and any pour subject to significant load. Use #4 rebar (1/2 inch diameter) at 18-inch spacing for residential slabs. Wire mesh (welded wire fabric) is used for flatwork like driveways, walkways, and patios to control shrinkage cracking. Place all reinforcement at mid-depth — resting mesh on the ground and hoping it "floats up" during the pour is a common mistake that leaves it at the bottom where it does little good.
A compacted gravel base (typically 4–6 inches of clean crushed stone, 3/4-inch minus) provides drainage, prevents frost heave, and creates a stable, uniform bearing surface. Never pour concrete directly on undisturbed native soil without checking bearing capacity. Organic material (topsoil, clay, silt) beneath a slab will compress and settle, causing the slab to crack. Compact the gravel in 3-inch lifts using a plate compactor — hand tamping is insufficient for large areas.
A 10×10 slab at 4 inches thick = 1.23 cubic yards = 33.3 cubic feet. An 80 lb bag yields approximately 0.60 cubic feet of mixed concrete, so you need about 56 bags of 80 lb (or 74 bags of 60 lb). Ready-mix is a far better choice for any slab this size — the labor of mixing 56 bags is substantial and risks inconsistent mix quality.
3,000 PSI is the minimum for residential driveways. 4,000 PSI is recommended for driveways that will see heavy vehicles, snow plows, or de-icing salts. In cold climates, use air-entrained concrete with 5–7% air content — the microscopic air bubbles accommodate freezing water expansion and prevent surface scaling.
Footings must extend below the frost line — the depth at which the ground freezes in winter. Frost depth varies from 12 inches in southern states to 72+ inches in northern Canada. Check your local building code for the required frost depth. Footings above the frost line will heave in winter and settle in spring, cracking the structure above.
You can pour in cold weather with proper precautions: use hot water in the mix, order air-entrained concrete, and protect the pour with insulating blankets for at least 7 days. Never pour on frozen ground — thaw the subgrade first. Below 20°F (-7°C), the risk of irreversible freeze damage is high even with precautions.
Foot traffic: 24–48 hours. Vehicle traffic: 7 days minimum, 28 days for full design strength. Don't use chemical de-icers (salt) in the first winter after a pour — they cause surface scaling on young concrete.
Common questions answered — straight from the job site.
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