Concrete Slab Cost Calculator
A concrete slab quote has three numbers hiding inside it: the concrete itself, the labor to form and finish it, and the site prep. This tool pulls them apart. Enter your slab size and thickness, set the per-yard ready-mix price and the installed rate per square foot, and you'll see what the material should cost versus what the finished job runs, plus the bag count if you're pouring it yourself. Walk into the quote conversation already knowing the shape of the answer.
What a slab actually costs, in three layers
Every slab price is really three stacked numbers: material (the concrete itself), labor (forming, pouring, finishing), and site work (grading, base, access). Quotes hide the split; this tool exposes it. Set your local ready-mix price and an installed rate, and you can see how much of the quote is the concrete and how much is everything wrapped around it.
For planning: plain gray concrete runs $4 to $8 per square foot installed across most of the US. Material alone is usually $1.50 to $2.50 of that. The rest is the crew, and a good finishing crew earns it, because concrete only gives you one chance.
Installed cost for common slab sizes
Figured at the $4 to $8 range with a $6 midpoint, 4 inches thick. Your market sets the real number; plug your quote into the tool to compare.
| Slab size | Square feet | Typical range | Midpoint |
|---|---|---|---|
| 10 x 10 | 100 | $400 - $800 | $600 |
| 12 x 16 | 192 | $770 - $1,540 | $1,150 |
| 20 x 20 | 400 | $1,600 - $3,200 | $2,400 |
| 24 x 24 | 576 | $2,300 - $4,600 | $3,460 |
| 30 x 30 | 900 | $3,600 - $7,200 | $5,400 |
| 30 x 40 (shop) | 1,200 | $4,800 - $9,600 | $7,200 |
What moves a quote up or down
| Factor | Effect on price |
|---|---|
| Thickness 4 in to 6 in | +30-50% on material, +10-20% overall |
| Rebar grid vs wire mesh | +$0.35-$1.00 per sq ft |
| Tear-out of old slab | +$1-$3 per sq ft |
| Poor access (no truck reach, pump needed) | +$500-$1,000 flat |
| Stamped or colored finish | jumps to $12-$18 per sq ft |
| Grading and fill on a slope | varies most of anything, get it itemized |
The pattern in every line: the concrete is the cheap part. The conditions around it set the bill, which is why two neighbors with identical slabs can pay 40% apart.
The DIY math, honestly
A 20 by 20 slab needs about 5.4 yards. Ready-mix at $155 runs $840 delivered, and the bag equivalent (about 245 bags at 80 lb) runs $1,700-plus and a weekend you won't get back, so the truck wins on material either way. Doing the labor yourself saves the $1,500 or so between material and installed price, but a 400-square-foot pour is past what a first-timer should finish alone. Two experienced friends, rented power screed and trowel, and a cool morning: maybe. A finishing crew: money well spent.
Size the material half of the job in the concrete calculator, and check what a full truck holds in our concrete truck guide.
Getting quotes that mean something
- Ask for the same spec from every bidder: thickness, PSI (3,500 to 4,000 for driveways), reinforcement, base depth, and joint plan. Quotes only compare if the slab does.
- Get the site work itemized. "Prep" hiding in one line is where surprise costs live.
- Ask who pulls the permit. Driveways and garage slabs need one in most towns, and approaches into the street have their own rules.
- Confirm cure time in writing. No vehicles for 7 days is standard; full strength takes 28.
Common questions
Most plain slabs land between $4 and $8 per square foot installed. A 20x20 runs $1,600 to $3,200, a 30x30 at the common 4 to 5 inch driveway spec runs $3,600 to $7,200. Stamped or colored finishes push past $12.
Around 12.2 cubic yards of concrete, roughly $1,900 in material at $155 a yard, and $3,600 to $7,200 installed depending on your market and site prep. Enter 30 by 30 above to price it at your local rates.
On material alone, yes, roughly half the installed price. But a slab pour is unforgiving: concrete sets on its schedule, not yours. DIY makes sense up to a small pad; past a few yards, hire the finishing crew.
Thickness, reinforcement, grading, and access. A sloped site that needs fill, a backyard the truck can't reach, or a 6-inch spec with rebar can each add 20 to 50% over the base rate.
Estimates for planning. Verify against your supplier's units and your local building codes before ordering or building. For anything structural, follow your engineer or local code.