Concrete Slab Cost Calculator – Patio & Floor Estimates | CalcLoft
Estimate what a concrete slab costs for a patio, shed pad or floor — materials by the square foot, concrete volume, plus base prep and labor.
How to estimate a concrete slab cost
For a simple rectangular slab, the estimate has two parts: the concrete materials per square foot, and the base prep and labor around the pour. Materials cost = slab area × price per sq ft, where the area is length × width. Most small slabs then need roughly 15–30% extra for base prep, forms and labor.
Example: a 10 × 10 ft slab is 100 sq ft. At $6 per sq ft the materials come to about $600, and adding the typical 15–30% gives $690–$780 total.
How much concrete does the slab need?
To check the concrete volume: cubic feet = area × thickness ÷ 12, then divide by 27 for cubic yards. A 10 × 10 ft slab at 4 in thick holds about 1.23 cubic yards. Concrete is sold by the yard, so round up to the nearest half yard — order about 1.5 cu yd here. Every extra inch of thickness adds about 25% more concrete.
Concrete slab cost examples ($6 per sq ft, 4-inch slab)
| Slab size | Area | Concrete (4 in) | Materials est. | Total with 15–30% |
|---|---|---|---|---|
| 10 × 10 ft | 100 sq ft | 1.23 cu yd | ≈ $600 | $690–$780 |
| 12 × 12 ft | 144 sq ft | 1.78 cu yd | ≈ $864 | $994–$1,123 |
| 20 × 20 ft | 400 sq ft | 4.94 cu yd | ≈ $2,400 | $2,760–$3,120 |
| 24 × 24 ft | 576 sq ft | 7.11 cu yd | ≈ $3,456 | $3,974–$4,493 |
These are estimates only — not local quotes. Prices vary by region, subbase conditions, rebar, finish and how far the batch plant is from the job. Use the calculator above with your own rate, then confirm with a local supplier or contractor.
What changes the cost the most?
Thickness drives concrete volume, and region drives labor: a 5 in slab needs about 25% more concrete than a 4 in slab, and a 6 in slab about 50% more. Gravel base, rebar or wire mesh, forms and demolition of an old slab all add cost on top of the numbers above. A thicker slab or a sloping, hard-to-reach site usually lands at the high end of the 15–30% range.
Related guides
Concrete slab cost FAQ
How much does a 10×10 concrete slab cost?
A 100 sq ft slab at the default $6 per sq ft comes to about $600 in materials. Adding the typical 15–30% for base prep and labor gives roughly $690–$780. Treat this as an estimate — regional labor rates, subbase and finish choices can move real quotes higher or lower.
Should I pour 4 inches or 5 inches?
4 in is standard for patios, walkways and shed pads on solid ground. Go 5–6 in for driveways or anything supporting vehicles. Each extra inch adds about 25% more concrete, so thicker slabs cost more in materials — the cubic-yard line in the calculator shows the difference.
What does the per-sq-ft price include?
For a typical flat slab, the per-sq-ft rate covers the concrete mix plus standard placement and finishing. It does not include site prep, gravel base, rebar or wire mesh, forms, saw-cutting or demolition — that's why the calculator adds 15–30%, and why a local quote always beats an online estimate.
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