Concrete Slab Cost Calculator
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About the Concrete Slab Cost Calculator
Concrete is sold by volume — cubic yards in the US, cubic meters most elsewhere — so a slab's material cost is just geometry times your local rate. The geometry is exact; the rate is the honest variable, moving with cement prices, fuel, distance from the plant, and load size. That's why this tool takes your quoted price as an input rather than pretending a national average applies to your driveway.
Two costs people forget to separate: the concrete and the installation. The pour itself is often only 40–60% of a contractor's slab quote — labor, forming, base gravel, reinforcement, and finishing carry the rest. This page prices the material precisely and gives you the framework for judging the rest of the quote.
Just need the volume without pricing? That's our Concrete Calculator
The Cost Formula
Geometry × local price:
Cost = (L × W × thickness ÷ 27, in yd³) × price/yd³ × (1 + waste%)
Worked example: a 10 × 10 ft patio at 4 inches = 100 × 0.333 ÷ 27 = 1.23 cubic yards. At a quoted $150/yd³ with 5% waste: 1.23 × 150 × 1.05 ≈ $195 of concrete. The same math in metric: volume in m³ × price per m³.
Common Slabs, Worked at an Example Rate
Volumes are exact; the dollar column uses an example $150/yd³ + 5% waste — rescale to your quote (at $180/yd³, multiply by 1.2):
| Slab | Thickness | Volume | Concrete @ $150/yd³ |
|---|---|---|---|
| 10 × 10 ft patio | 4 in | 1.23 yd³ | ≈ $195 |
| 12 × 12 ft shed base | 4 in | 1.78 yd³ | ≈ $280 |
| 20 × 20 ft garage | 4 in | 4.94 yd³ | ≈ $778 |
| 20 × 20 ft driveway | 6 in | 7.41 yd³ | ≈ $1,167 |
Note the thickness lever: the same 20×20 footprint costs 50% more at 6 inches than 4 — and driveways carrying vehicles genuinely need the thickness. Under-thickening to save a few hundred dollars is the classic slab regret.
Beyond the Concrete: What a Full Installation Adds
A contractor's quote stacks on top of the material:
- Base preparation — excavation and compacted gravel are essential on most soils.
- Forms and finishing labor — often rivaling the concrete cost itself.
- Reinforcement — wire mesh or rebar, per your span and load.
- Short-load fees — small pours below roughly 3 yd³ often carry a truck surcharge.
- Extras that are cheap now and expensive later: vapor barrier, control joints, sealing.
Rule of thumb for sanity-checking quotes: if this calculator says $780 of concrete and the installed quote is $2,000–2,600, that's a normal labor-and-prep multiple. A quote at 6× material deserves questions; so does one barely above material cost.
Frequently Asked Questions
How do I calculate the cost of a concrete slab?
Volume × your local ready-mix price: length × width × thickness gives cubic feet, divide by 27 for cubic yards, multiply by the per-yard price from a local supplier, and add 5–10% waste. A 10×10 ft slab at 4 inches is 1.23 yd³ — about $195 at a $150/yd³ quote.
Why doesn't this calculator just tell me the concrete price?
Because ready-mix pricing is intensely local — it moves with cement markets, fuel, plant distance, and order size, and any published number goes stale fast. One call to a nearby supplier gets your real rate; entering it here turns exact geometry into an exact material cost instead of a guess.
How much does a 20x20 concrete slab cost?
At 4 inches thick it's 4.94 cubic yards of concrete — about $778 of material at an example $150/yd³ with waste. A full professional installation (base, forms, labor, finishing) commonly lands at 2.5–3.5× the material figure, so a $2,000–2,700 installed quote for that slab is within normal range.
What thickness should my slab be?
Common practice: 4 inches for patios, walkways, and shed bases; 5–6 inches for driveways and anything carrying vehicles; more for heavy equipment. Thickness is the biggest single cost lever — 6 inches costs 50% more than 4 — but under-building a driveway saves once and cracks forever. Confirm against local code for structures.
Does the estimate include labor and base preparation?
No — deliberately. This tool prices the concrete itself, exactly. Labor, excavation, gravel base, forms, reinforcement, and finishing vary by site and region far more than material does; the 'Beyond the Concrete' section gives you the checklist and the normal installed-cost multiple (roughly 2.5–3.5× material) for judging quotes.
Cubic yards or cubic meters — which should I use?
Whichever your supplier quotes. US ready-mix sells by the cubic yard; most other countries quote per cubic meter. This calculator accepts either price basis and reports the volume in both units — 1 cubic yard is about 0.765 cubic meters.
Methodology. This calculator uses standard construction and material-estimation formulas. It is reviewed and maintained by the Vast Calculators editorial team.
Last updated · July 2026
Results are estimates for general use; verify critical figures independently.