Concrete slab cost by size
Estimates from this page's default prices for a 4 in slab with welded wire mesh, 4 in of gravel base, a broom finish and average site prep. Change the defaults above to match quotes or supplier prices near you.
| Slab | Concrete | Installed | Per sq ft |
|---|---|---|---|
| 10 × 10 ft | 1.36 cu yd | $1,200–$1,850 | $15.25 |
| 12 × 12 ft | 1.96 cu yd | $1,550–$2,300 | $13.30 |
| 20 × 20 ft | 5.43 cu yd | $3,400–$5,100 | $10.66 |
| 24 × 24 ft | 7.82 cu yd | $4,600–$6,850 | $9.94 |
| 30 × 30 ft | 12.22 cu yd | $6,900–$10,350 | $9.59 |
Small slabs cost more per square foot. Setup time is the same for any pour, and an order under 6 yards pays a short-load fee.
Concrete cost per yard
Ready-mix plants price concrete by the cubic yard, delivered. Our default is $170 per yard, which you can change above. Ask the plant for its price for the mix you need, since stronger mixes and additives cost more.
Most plants add a short-load fee to small orders. Our default is $150 on orders under 6 yards. That fee changes what you really pay per yard: about $270 per yard delivered for a 10 × 10 slab, $197 for a 20 × 20, and the plain $170 for a 30 × 30. Concrete is ordered in quarter yards here, with 10% extra for spillage and an uneven base, the same as our concrete calculator.
Installed, the whole job comes to about $706–$1,123 per cubic yard of concrete placed in these examples, because labor, base and forms cost more than the concrete itself.
Cost of a 30x30 slab, 4 inches thick
A 30 × 30 ft slab 4 in thick needs about 12.22 cubic yards of concrete. With welded wire mesh it comes to about $6,900–$10,350 installed with these defaults. With #4 rebar on an 18 in grid it comes to about $7,850–$11,800. That size is common for a detached garage or shop, which many towns treat as a structure needing a permit and sometimes thicker edges, so check local rules.
Thickness and finish
For a 20 × 20 slab, going from 4 in to 5 in thick raises the estimate to about $3,600–$5,400, and 6 in to about $3,850–$5,800. A stamped and colored finish brings it to about $5,000–$7,500, and exposed aggregate to about $3,950–$5,900.
What changes the price
- Size: concrete, base and labor scale with area, but setup and the short-load fee don't, so small slabs cost more per square foot.
- Thickness: each extra inch adds about a quarter more concrete than a 4 in slab.
- Reinforcement: rebar costs about three times as much as wire mesh per square foot in this model.
- Site prep: removing sod and soil first adds labor and an excavation and haul-off charge.
- Access: if the truck can't reach the forms, a pump adds a fee per pour.
- Permits: many towns require a permit for slabs under structures. Call 811 before anyone digs.
How this estimate works
Concrete is length × width × thickness plus 10%, ordered in quarter yards at $170 per yard, with a $150 short-load fee under 6 yards. Gravel base is crusher run at 1.5 tons per cubic yard plus 15% for compaction, $38 a ton and $85 delivery. Forms are $1.50 per foot of edge. Wire mesh is $0.35 per sq ft and rebar $1.05, from our rebar calculator's count for #4 bar at 18 in. Stamped finishes add $1.25 per sq ft in materials.
The contractor's markup on materials is 20%. Labor is 4 hours of setup plus, per 100 sq ft, 5 hours to form, pour and finish, 1.5 hours of site prep, and time for mesh, rebar or decorative finishes. Labor is charged at $70 an hour, a billed rate that includes the contractor's overhead and profit, not a crew wage. The range is the result minus 20% to plus 20%, because real quotes vary with region, season and the contractor. Change any of these above.
Homewyse puts a cement slab at $10.33–$12.65 per sq ft installed (Homewyse, May 2026), for a 4 in fiber-reinforced slab up to 500 sq ft, without excavation or a gravel base. This estimate's default 20 × 20 slab comes to about $10.66 per sq ft, including 4 in of gravel base.
Getting quotes
Get at least three quotes for the same size, thickness, base depth, reinforcement and finish. Ask whether the price includes excavation, haul-off, a pump and the permit, and how control joints will be cut. If a quote is far below this estimate, ask what's left out.
Questions
How much does a 20x20 concrete slab cost?
With this page's defaults, a 20 × 20 ft slab 4 in thick with wire mesh comes to about $3,400–$5,100 installed, or about $10.66 per sq ft. It needs about 5.43 cubic yards of concrete.
How much is a yard of concrete?
Our default is $170 per cubic yard of ready-mix, delivered, which you can change to your plant's price. Small orders often pay a short-load fee on top, which raises the real price per yard.
How much does a 12x12 concrete slab cost?
A 12 × 12 ft slab 4 in thick comes to about $1,550–$2,300 installed with these defaults, or about $13.30 per sq ft.
Is it cheaper to pour a slab yourself?
Usually, if you have help and the tools. For a 20 × 20 slab, materials come to about $1,772 in this estimate, against $3,400–$5,100 installed. Concrete sets fast, so plan for several people on pour day.