Concrete Slab Cost Calculator

How much does a concrete slab cost?

Poured concrete slabs in 2025 cost $5–$12 per square foot for a standard 4" reinforced slab. A 20'×20' (400 sq ft) slab typically runs $2,000–$4,800 including forms, gravel base, rebar, and finishing. Decorative options like stamped, colored, or polished concrete push $10–$25/sq ft. Our calculator estimates by slab dimensions, thickness, reinforcement, and ZIP-adjusted labor.

Cost breakdown

• Concrete material — 30–40%. Ready-mix ~$150–$200 per cubic yard delivered; a 4" slab needs one cubic yard per 80 sq ft.
• Labor — 30–45%. Forming, placing, finishing, curing.
• Base prep — 10–15%. 4"–6" of compacted crushed stone $1–$2/sq ft.
• Reinforcement — 5–10%. #3 or #4 rebar grid $0.50–$1.00/sq ft; wire mesh cheaper but weaker.
• Vapor barrier, control joints, sealer — 5–10%.

Bigger slabs cost less per square foot because setup and truck delivery are fixed costs.

Common slab uses and specs

• Shed pad, HVAC pad — 3–4" thick, wire mesh, no rebar. $5–$8/sq ft.
• Patio — 4" thick, rebar or fiber, control joints every 8–10 ft. $6–$10/sq ft.
• Driveway approach — 5" thick, #4 rebar 12" o.c., stronger base. $8–$14/sq ft.
• Garage floor — 4" thick, rebar, floor drain slope, moisture barrier. $6–$12/sq ft.
• Foundation slab-on-grade — 4–6" thick, thickened edges (12"×12"), engineered rebar. $8–$14/sq ft when part of a build.

How to use the calculator

Enter slab dimensions and thickness, select reinforcement type (fiber, mesh, or rebar), whether the site needs excavation, and your ZIP. The estimate includes concrete, base, forms, reinforcement, standard broom finish, and control joints.

What the estimate doesn't include

• Excavation over 6" deep — Add $2–$5/sq ft for machine dig and haul.
• Root or rock removal — Case by case.
• Post-tension cable slabs — Common on expansive soils; adds 25–40%.
• Decorative treatments — Stamped, colored, exposed aggregate, polished, or stained; $4–$15/sq ft on top of the standard finish.
• Permits — Typically required for slabs over 30 sq ft or when attached to a structure; $50–$300.

Thickness and reinforcement — get this right

Under-speccing thickness and rebar is the #1 cause of cracked slabs. Rules of thumb:

• Foot traffic, occasional light loads: 4" with wire mesh or fiber
• Vehicles (driveways, garage): 5"+ with #4 rebar on 12" grid
• Heavy equipment (RV pads, workshops): 6"+ with #5 rebar

Add rebar over wire mesh anywhere near vehicle loads — mesh doesn't hold slabs together when they crack.

Control joints — necessary, not optional

Concrete cracks. The question is where. Control joints (saw-cut or tooled) force cracks to happen at planned lines. Rules:

• Space joints at 24–30× slab thickness (so ~8–10 ft on a 4" slab)
• Cut within 24 hours of pour (dry-cut) or within 12 hours (wet-cut)
• Depth at least 1/4 of slab thickness

Skipping control joints saves nothing and creates ugly random cracks within a year.

Weather and timing

Concrete doesn't like extremes. Pour when air temps are 40–90°F for 24 hours after placement. In cold weather, concrete needs blankets and calcium chloride accelerators (adds cost). In hot dry weather, retarders and constant wet-curing prevent surface cracks. Reputable contractors won't pour outside 40–90°F without proper mitigation — pushing them to do so is how you get a bad slab.

Common ways slabs fail

1. Improper base. Uncompacted or muddy base guarantees settlement cracks.
2. No vapor barrier. Slabs on grade need 10-mil poly under the concrete or the slab wicks moisture forever.
3. Wrong reinforcement. Mesh instead of rebar under vehicle loads.
4. Missed control joints. Cracks anywhere they want.
5. Sealing too early or too late. Cure 28 days minimum, seal within 90 days.

Regional cost variation

Concrete price per yard varies $130 (Texas, Midwest) to $230+ (California, Northeast, Hawaii). Labor rates vary 2–3× between rural and metro. Slabs are one of the most locally-priced construction items; the calculator's ZIP-based multiplier reflects this closely.

Save without shortcuts

• Combine pours. Multiple slabs (patio + shed + walk) with one truck delivery saves the short-load fee ($75–$200 per yard under a full load).
• Weekday pours. Saturday premiums are 10–20%.
• DIY excavation. A rented mini-excavator ($350/day) can prep a 400 sq ft pad in a day.
• Standard broom finish. Decorative finishes are 3–5× the cost of standard.
• Skip color, add stain later. Concrete acid stain applied a year after cure often looks better than integral color for less.

Decorative options ranked

• Broom finish: Baseline
• Exposed aggregate: +$2–$4/sq ft; slip-resistant
• Sawcut geometric patterns: +$1–$3/sq ft
• Stamped concrete: +$4–$10/sq ft; imitates stone/brick
• Acid stain / color: +$2–$5/sq ft
• Polished concrete: +$6–$12/sq ft; interior only, needs mechanical grind

DIY vs. hire

Slabs under 100 sq ft, single truck (~10 yards or less), and level ground are DIYable for handy homeowners with 3–4 helpers. Anything larger or with grade changes should be hired out — a bad pour is unfixable except by demo and redo.