Cost data reviewed August 2026. Sources listed at the foot of this page.
What a concrete slab actually costs
A standard 4-inch residential slab runs $6 to $8 per square foot installed in most of the United States. That figure covers grading, forming, a compacted gravel base, wire mesh reinforcement, the concrete itself, the pour and a broom finish. On a typical 30 × 30 ft garage pad — 900 square feet — that works out to roughly $5,400 to $7,200.
Labor is 40 to 50 percent of the total. That split matters more than most cost guides let on, because it is the half that moves when you move: material prices are close to national, while a crew’s day rate is not. The calculator applies your regional factor to the labor half only, which is why a Mid-Atlantic slab comes out around 7 percent higher rather than the full 15 percent you might expect from a blunt regional multiplier.
Thickness changes the material, not the crew
Going from a 4-inch to a 6-inch slab adds 50 percent more concrete but almost no extra labor — the same forming, the same screeding, the same finishing time. The calculator scales only the material portion with thickness for that reason. As a rough guide:
| Thickness | Typical use | Concrete per 100 sq ft |
|---|---|---|
| 4 inches | Patios, sheds, walkways, footpaths | 1.23 cu yd |
| 5 inches | Driveways, light vehicle parking | 1.54 cu yd |
| 6 inches | Garages, RV pads, heavy vehicles | 1.85 cu yd |
| 8 inches | Equipment pads, commercial traffic | 2.47 cu yd |
Ordering ready-mix: the short-load trap
Ready-mix concrete delivers at roughly $120 to $150 per cubic yard within about 20 miles of the plant, and a full 10-yard truck runs $1,170 to $1,450. The catch is that anything under 10 cubic yards attracts a short-load fee of about $40 to $60 per yard — which on a small pour can add more than a third to the bill.
Note that published per-yard prices vary widely by source. HomeGuide and Angi both cluster at $110–$150; ConcreteNetwork reports $160–$195 from supplier quotes that appear to bundle delivery and short-load charges. We use $120–$150 as the base and show fees separately, because a number that quietly includes fees is one you cannot plan against.
Always order more than the theoretical volume. A sub-grade that dips half an inch across a 900 sq ft pad swallows an extra 1.4 cubic yards, and a truck that leaves before the slab is full is an expensive mistake. Ten percent is the standard allowance.
What pushes a slab above the range
- Excavation. The base price assumes a few inches of grading. Cutting into a slope, removing tree roots or hauling off spoil is separate work.
- Rebar instead of mesh. Standard pricing assumes welded wire mesh. A rebar grid for a heavier load adds material and tying labor.
- Decorative finishes. Stamped, stained and polished concrete run well above a broom finish — often double.
- Access. If the truck cannot reach the pour, someone is running wheelbarrows or you are paying for a pump.
- Thickened edges and footings. A slab carrying a wall needs a deeper perimeter, which is extra concrete and extra forming.
Common questions
How much concrete do I need for a 20x20 slab?
A 20 × 20 ft slab is 400 square feet. At 4 inches thick that is 4.94 cubic yards theoretical, so you would order about 5.4 cubic yards allowing 10 percent for sub-grade variation. At 6 inches thick it is 7.4 cubic yards theoretical, or roughly 8.1 to order.
Is it cheaper to pour a slab yourself?
The concrete is typically 50 to 60 percent of the installed price, so a DIY pour saves real money on paper. In practice, forming, screeding and finishing are time-critical skills — you get one window before the concrete sets, and a badly finished slab cannot be undone. Small pads are a reasonable DIY project. Anything structural, load-bearing or larger than about 200 square feet usually is not.
How thick should a garage slab be?
Six inches is the common specification for a residential garage carrying passenger vehicles, with wire mesh or a rebar grid and a compacted gravel base. Four inches is adequate for a shed or patio. Check your local code, which may specify a minimum.
Why is my quote higher than this calculator?
The most common reasons are excavation beyond simple grading, poor site access, a decorative finish, thickened edges for a structure, or a small pour where fixed costs and the short-load fee dominate. Regional labor rates in a specific high-cost metro also run well above the broad regional average this calculator uses.