Concrete slab cost typically runs $4 to $8 per square foot installed in 2026. A 20×30 ft slab runs about $2,400–$4,800, and a 30×30 ft slab about $3,600–$7,200. Your price depends on thickness, reinforcement, site preparation and local labor rates. Dense metro areas like New York City usually land above these national figures.
This guide breaks down each cost driver so you can build a realistic budget before you ask for quotes.
Average concrete slab cost per square foot
The installed price covers concrete, forms, base material, reinforcement, finishing and labor. National cost guides put a standard 4-inch slab at roughly $5 per square foot. Thicker slabs cost more because they need more concrete and often more steel.
| Slab thickness | Average installed cost per sq ft | Typical uses |
|---|---|---|
| 4 inches | about $5 | Patios, walkways, shed floors, basement floors |
| 6 inches | about $6 | Driveways, garage floors, hot tub pads |
| 8 inches | about $8 | Heavy equipment pads, some commercial floors |
Concrete slab cost by size
To estimate a slab, multiply its area by the per-square-foot range:
- 10×10 ft (100 sq ft): about $400–$800
- 20×20 ft (400 sq ft): about $1,600–$3,200
- 20×30 ft (600 sq ft): about $2,400–$4,800
- 30×30 ft (900 sq ft): about $3,600–$7,200
Very small slabs often cost more per square foot. Contractors charge minimum fees for mobilization, forming and finishing, whatever the size.
What you pay for: the cost breakdown
Concrete material
Ready-mix concrete averages about $125 per cubic yard, with a typical range of $110–$165 depending on strength (PSI) and region. One cubic yard covers about 81 square feet at 4 inches thick.
Orders smaller than a full truck (around 8–10 cubic yards) usually carry a short-load fee. That's about $40 per yard or a flat $60–$110. For very small pours, bagged concrete can be cheaper. See our guide to concrete bags vs ready-mix.
Reinforcement
- Welded wire mesh: about $0.35 per sq ft
- Steel rebar grid: about $2–$3 per sq ft
- Thickened edges: about $1–$2 per sq ft
Rebar adds strength against cracking and heavy loads. Wire mesh mainly holds cracks tight. Use our Rebar Calculator to count bars for your grid spacing.
Vapor barrier and insulation
A polyethylene vapor barrier under interior slabs costs about $0.50 per sq ft. Rigid foam insulation under heated spaces adds about $0.50–$2 per sq ft. Energy codes in cold climates, including most of New York State, may require slab-edge or under-slab insulation for living spaces.
Site preparation
Grading, excavation and a compacted gravel base are often the most variable line items. Expect these costs to climb when:
- The site slopes and needs fill or a retaining edge
- Old concrete or tree roots must be removed
- Soil is soft clay and needs a thicker base
- Equipment access is tight, as in many city backyards
Finishes
A plain broom or trowel finish is included in base pricing. Decorative options add cost:
- Stain or color: about $3.50–$7.50 per sq ft
- Stamping: about $10–$20 per sq ft
- Sealer: about $1–$2 per sq ft
How to estimate your own slab
Work through these four steps before you call a contractor.
- Measure the area. Multiply length by width in feet. A 20×20 slab is 400 sq ft.
- Convert thickness to feet. 4 inches = 0.333 ft; 6 inches = 0.5 ft.
- Find the volume. Area × thickness ÷ 27 = cubic yards. A 400 sq ft slab at 4 inches is 4.94 cubic yards.
- Add waste. Order 5–10% extra for uneven ground and spillage. That puts this example at about 5.25–5.5 yards.
At $125 per yard plus a short-load fee, materials for this example run about $700–$900. Labor, base, reinforcement and finishing bring the installed total into the $1,600–$3,200 range above. The Concrete Slab Calculator does this math for you, including bags and waste.
Concrete slab foundation cost vs. flatwork
A slab foundation for a house or addition is not the same as a patio slab. Foundation slabs need engineered footings, thickened edges, under-slab plumbing and inspections. They are priced as part of the foundation system. Use this guide for flatwork: patios, sheds, garage floors and pads. For structural work, a design professional should specify the slab.
Ways to lower concrete slab cost
- Pour in one visit. Combining a patio and walkway into one pour avoids two short-load fees.
- Choose a broom finish. Decorative stamping can double the price.
- Do the demolition yourself if it's safe and allowed. Removing an old shed or pavers saves labor hours.
- Get three written quotes that list thickness, PSI, reinforcement and base depth, so you compare like for like.
Permits and local rules
Many towns require a permit for slabs that support structures, such as garages, additions and large sheds. Some require one for any slab over a set size. In New York City, owners repairing the public sidewalk need a separate NYC DOT permit. Check with your local building department before you pour. Our NYC building permits guide explains how city filings work.
Frequently asked questions
How much does it cost to pour a 20×20 concrete slab?
About $1,600–$3,200 for a standard 4-inch slab, based on $4–$8 per square foot. Thicker slabs, rebar or decorative finishes push the price higher.
Is it cheaper to pour concrete yourself?
You can save on labor, roughly half the installed cost. But forming, placing and finishing a large slab before it sets is hard work. Mistakes are expensive to fix. DIY makes most sense for small pads under about 100 sq ft.
How thick should a concrete slab be?
Four inches suits patios and walkways. Garage floors and driveways usually need 5–6 inches. Your local code or engineer has the final say for structural slabs.
Does rebar add a lot to the cost?
A rebar grid adds about $2–$3 per square foot. For a 400 sq ft slab, that's roughly $800–$1,200.
National averages, planning estimates only; get local quotes.
