Cost to Pour a 400 Sq Ft Concrete Slab: $2,180 to $5,620
A 400 sq ft concrete slab, poured 20x20 at 4 inches with wire mesh on a 4-inch crushed-stone base and broom-finished, costs about $3,360 installed. From the lowest published prices to the highest the range is $2,180 to $5,620 ($5.45 to $14.06 per sq ft). It takes 4.94 cubic yards of concrete. A 6-inch slab with a rebar grid, the usual spec for a garage or driveway, is about $4,690.
400 Sq Ft Slab Cost by Thickness and Reinforcement
The same 20x20 footprint can cost twice as much depending on what it has to carry. The table prices five common specifications with the same model: published ready-mix, stone and materials prices, crew hours at Bureau of Labor Statistics wages, and a stated overhead and margin.
| 20 x 20 spec | Concrete | Low | Typical | High |
|---|---|---|---|---|
| 4-inch, no reinforcement | 4.94 yd | $1,990 | $3,100 | $5,240 |
| 4-inch, wire mesh (patio) | 4.94 yd | $2,180 | $3,360 | $5,620 |
| 4-inch, 4,000 PSI, mesh (driveway) | 4.94 yd | $2,210 | $3,410 | $5,700 |
| 6-inch, 4,000 PSI, rebar (garage) | 7.41 yd | $3,170 | $4,690 | $7,430 |
| 8-inch, 4,000 PSI, rebar (heavy load) | 9.88 yd | $3,880 | $5,690 | $9,360 |
All rows: broom finish, crushed-stone base (4 inches, or 6 inches under the 8-inch slab), national prices. Low uses the lowest published price and our lowest labour assumption at every step; high uses the highest.
The shape matters much less than the spec. A 400 sq ft slab poured as a square, a 16x25 rectangle or a 10x40 strip needs the same concrete; only the form boards around the edge change. 20 x 20 (square): 80 ft of forms, about $3,360; 16 x 25: 82 ft of forms, about $3,370; 10 x 40 (long strip): 100 ft of forms, about $3,380.
Why 400 Sq Ft Usually Escapes the Short-Load Fee
Ready-mix suppliers add a charge to small orders. The two published lists we use set the line in different places: Gehring (Columbus, Nebraska) charges $50 on loads under 4 yards, and Scenic City Ready Mix (Tennessee) charges $100 at 5 yards or less, plus another $100 at 2 yards or less.
A 4-inch 20x20 slab is 4.94 cubic yards, so with overage the order is about 5.19 to 5.43 yards: over both thresholds. Half that area, a 200 sq ft slab at 2.47 yards, pays them. Published 3,000 PSI prices run $127.05 to $165.00 a yard, so the concrete and truck charges for a 400 sq ft slab come to $659 to $1,315, about 23% of the typical total. The rest is the stone base, steel, forms, the crew and the contractor’s overhead and margin.
Wire Mesh vs Rebar at 400 Sq Ft
The model International Residential Code does not require reinforcement in a slab on the ground; where steel is used, R506.2.4 only says it must be supported so it stays in place during the pour. Mesh and rebar are a design and durability choice. At this size, 6x6 10-gauge mesh costs about $96 in materials and adds about $260 to the typical installed price. A #4 rebar grid at 18 inches each way costs about $297 in bar and chairs and adds about $760 installed, because tying a grid takes more crew time.
For a slab that will carry vehicles, contractors normally specify a thicker slab with rebar, which is the 6-inch row in the table above. Fiber-reinforced mix is a third option; we have not yet sourced a price for it, so it is not in these figures. See rebar vs wire mesh and the fiber-reinforced concrete page.
Base and Vapor Retarder for a 400 Sq Ft Slab
A 4-inch compacted stone base under 400 sq ft is 4.94 cubic yards in place, and about 5.9 yards loose before compaction. At four suppliers’ published crusher-run prices that stone costs $261 to $443, and it is included in the totals above. Digging out the old soil and hauling it away is not: it depends on how much has to come out and where it can go, so get it priced on the quote.
IRC R506.2.3 calls for a 6-mil vapor retarder under a concrete floor slab, with exceptions for garages, utility buildings and other unheated accessory structures, small unheated storage rooms and carports, and driveways, walks and patios not likely to be enclosed and heated later. Where it is needed, 6-mil polyethylene costs about $29 for 400 sq ft at Menards’ roll price. The site prep page covers grading and excavation.
How 400 Sq Ft Compares to Smaller and Larger Slabs
Every job carries fixed work whatever its size (layout, setting up, stripping forms, cleanup; our model allows 8 to 16 crew hours), and a small pour also pays the short-load fee, so the price per square foot falls as the slab grows. Same spec (4-inch, mesh, stone base) at five sizes:
| Size | Typical total | Per sq ft | Low to high |
|---|---|---|---|
| 100 sq ft (10 x 10) | $1,410 | $14.09 | $830 to $2,880 |
| 200 sq ft (10 x 20) | $2,100 | $10.49 | $1,300 to $3,760 |
| 400 sq ft (20 x 20) | $3,360 | $8.41 | $2,180 to $5,620 |
| 500 sq ft (20 x 25) | $4,050 | $8.09 | $2,650 to $6,630 |
| 1,000 sq ft (25 x 40) | $7,490 | $7.49 | $4,990 to $12,220 |
Use the size calculator for your exact dimensions, or check a quote you already have.
How We Price a Slab
Every installed price on this site comes from one model: published ready-mix and materials prices, plus crew hours priced at Bureau of Labor Statistics wages, plus overhead and margin. The low figure uses the lowest published input and our lowest assumption at every step; the high figure uses the highest. The crew hours, overage and margin are our own estimates, not published figures, and are listed below so you can check them against your quote. Worked example: a 20 x 20 ft (400 sq ft) slab (4-inch, 3,000 PSI, wire mesh, broom finish, 4-inch stone base).
| Line | Low | Typical | High | Basis |
|---|---|---|---|---|
| Ready-mix concrete | $659 | $754 | $896 | 4.94 cu yd plus 5 to 10% overage, at published per-yard prices |
| Delivery and small-load charges | $0 | $35 | $419 | Per-truck charges from the same price lists (10 yd per truck) |
| Crushed-stone base | $261 | $325 | $443 | 4 in compacted crusher run |
| Reinforcement | $96 | $96 | $96 | 6x6 10-gauge mesh panels, lapped |
| Form lumber | $30 | $45 | $61 | Perimeter boards, shared across reuses |
| Crew labour | $770 | $1,332 | $2,101 | Crew hours x BLS wages x employer costs |
| Overhead and margin | $363 | $776 | $1,606 | 20% to 40% on direct cost |
| Installed total | $2,180 | $3,360 | $5,620 | Rounded to the nearest $10 |
Not included: excavation and soil haul-off, removing an old slab, permits, pumping, decorative finishes and sealing. Totals are national; the calculators’ state option swaps in that state’s BLS wages and leaves concrete and materials at the published lists.
Published inputs (read 13 October 2026)
- Ready-mix, per cubic yard: 3,000 PSI $127.05 to $165.00, 4,000 PSI $132.00 to $175.00, from Supreme Concrete (Los Angeles, CA), Minimix Concrete (Pequannock, NJ), Gehring Construction & Ready-Mix (Columbus, NE, list dated 2026-01-01), Scenic City Ready Mix (Tennessee, list dated 2024-08-03).
- Small orders and trucks: short-load charge $50 under 4 yd (Gehring) or $100 at 5 yd or less, plus $100 more at 2 yd or less (Scenic City); per truck, no charge within 20 miles (Gehring), a $35 surcharge (Scenic City), or $363.88 Zone A delivery plus a $55 environmental fee (Supreme).
- Crushed-stone base: $44.00 to $74.75 per cubic yard from D & L Supply (Central New York, $44.00/yd), JMJ Companies (Lynchburg, VA, $39.50/ton), Golden Landscaping Supply (Cumming, GA, $50.00/ton), Yard Works Landscape Supply (Fort Mill, SC, $74.75/yd); per-ton prices converted at 2,450 lb per yard.
- Steel, forms, poly: #4 rebar 20 ft $8.99, 6x6 10-gauge mesh 4x8 panel $6.99, 2x6x12 $14.32, 2x4x16 $12.13, 6-mil poly 8 ft 4 in x 100 ft $59.99, rebar chair $0.33 (Menards online prices; Home Depot and Lowe’s pages could not be read that day). That works out to $0.24 per sq ft for mesh and $0.74 per sq ft for a rebar grid, materials only.
- Wages: BLS OEWS 47-2051 cement masons (May 2025) 25th percentile $22.60, median $27.41, 75th $32.15 an hour; 47-2061 construction laborers $18.57, $22.66, $28.72. Employer costs from BLS ECEC June 2026, construction industry ($51.96 total compensation per $36.13 of wages, x1.44): a crew hour costs $29.60 to $43.77.
Our assumptions (estimates, not published figures)
- Crew: half cement masons, half laborers.
- Setup per job: 8 to 16 crew hours (layout, stripping, cleanup).
- Per 100 sq ft: 4-inch 4 to 7 crew hours, 6-inch 5 to 8.5, 8-inch 6 to 10; add 0.5 to 1 for mesh or 1.5 to 2.5 for rebar.
- Concrete overage 5% to 10%; base stone ordered at 1.2x its compacted volume; form boards charged at half to all of their price.
- Overhead and margin 20% to 40% of direct cost.
- 6-inch and thicker slabs use 4,000 PSI mix; thinner slabs 3,000 PSI.
Sources: BLS OEWS 47-2051 cement masons (May 2025), BLS OEWS 47-2061 construction laborers (May 2025), BLS ECEC, construction (June 2026), ready-mix price lists from Supreme Concrete, Minimix Concrete, Gehring Construction & Ready-Mix, Scenic City Ready Mix, crusher-run prices from D & L Supply, JMJ Companies, Golden Landscaping Supply, Yard Works Landscape Supply, Menards mesh, rebar, lumber and poly prices, QUIKRETE Concrete Mix data sheet (bag yield), IRC R105.1, R105.2, R506.2.3 and R506.2.4. All read 13 October 2026. Crew hours, overage, overhead and margin are our estimates and are listed in the method above.