What Goes Into Concrete Slab Cost?
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.
How to Calculate Concrete Slab Cost
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.
Slab Costs 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.
What a Full Slab 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.