Concrete Cost Calculator

A 20 × 20 ft concrete slab at 4 inches deep needs about 4.9 cubic yards and costs roughly $740 in materials at national average pricing ($150/yd³ ready-mix).

10% is standard for slabs. Increase to 15–20% for irregular shapes or pump pours.
Finish costs are labor-only, added to material total.
Estimated Material Cost 740.74 $
Volume Yd3
4.94
Area Sqft
400
Bags80lb
223
Cost Low
$593
Cost High
$889
2 in
Calculate Rebar Needs
Rebar spacing
Bars lengthwise
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Bars widthwise
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Total linear feet
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20-ft sticks needed
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Price Trend: Ready-Mix Concrete

BLS Producer Price Index trend since 2015.

Source: BLS PPI (series PCU327320327320)

How We Calculated This

We multiply your slab dimensions (L × W × depth) to get cubic feet, convert to cubic yards (÷ 27), then multiply by the national average ready-mix price from FRED series PCU327320327320. Waste factor adds a percentage buffer. Finish costs are per-square-foot adders from contractor labor surveys. Rebar estimates assume a single-layer grid at your chosen spacing.

Real Project Cost Examples

Backyard patio

12 × 14 ft, 4 in

Concrete (2.3 yd³)
$345
Delivery
Included
Broom finish
Included
Total $345

Two-car driveway

20 × 24 ft, 5 in

Concrete (7.4 yd³)
$1,110
Delivery
Included
Broom finish
Included
Total $1,110

Stamped pool deck

30 × 15 ft, 4 in

Concrete (5.6 yd³)
$840
Stamped finish
$3,600–$8,100
Delivery
Included
Total $4,440–$8,940

Rookie Mistakes on This Project

Ordering the exact cubic yardage you calculated with no overage

Cost: Ready-mix trucks typically charge a short-load or return-trip fee — often equal to a full minimum load charge — if you call for a second delivery mid-pour

Fix: Order 10% over your calculated volume; leftover concrete is cheaper than a second truck and a cold joint

Ignoring the ready-mix supplier minimum charge

Cost: Most suppliers bill a full minimum (commonly 1 cubic yard) even for smaller orders — you pay for concrete you do not use

Fix: Call your supplier for their minimum before calculating; bag mix is more cost-effective for pours under roughly half a cubic yard

Getting one quote and treating it as the market price

Cost: Ready-mix prices vary by $30–$60 per cubic yard across suppliers in the same metro area, according to BLS PPI regional data

Fix: Get three quotes; use the national range shown on this page as a baseline to judge whether a quote is high

Forgetting to include labor in the total project budget

Cost: Finishing labor (screeding, floating, edging, sealing) typically runs $2–$4 per square foot on top of material cost — easily doubling the total for small slabs

Fix: Use this calculator for materials only; get a separate labor quote from a finisher before committing to a project budget

Pro Tips

Order 10% extra

Ready-mix trucks cannot take concrete back. Short pours mean cold joints, which crack. Round up.

Prep subgrade first

4 in of compacted gravel under 4 in of concrete prevents settling cracks. This is where most DIY slabs fail.

Pour temp matters

Below 50 °F concrete sets too slowly; above 90 °F it cures too fast and cracks. Schedule pours for 50–80 °F.

What Else You'll Need

  • Form lumber (2×4 or 2×6) — Enough to frame the full perimeter. Stake every 2–3 ft.
  • Gravel base (4 in) — Compactable aggregate, not pea gravel. Rent a plate compactor.
  • Vapor barrier (6-mil poly) — Required under interior slabs and any slab supporting a structure.
  • Rebar or wire mesh — Rebar at 18 in spacing for driveways; wire mesh acceptable for sidewalks.
  • Expansion joint material — ½ in fiber board where slab meets existing structure or another slab.
  • Curing compound or plastic sheeting — Apply immediately after finishing. Keep wet for 7 days minimum.

After the Pour

Control Joints

Spacing Slab thickness (in) × 2.5 = max spacing (ft). 4 in slab → joints every 10 ft.
Depth Cut ¼ of slab depth. 4 in slab → 1 in deep cut.
Timing Cut within 6–18 hours of finishing, before surface cracks form.

Source: ACI 302.1R-15, Section 8.3

Curing

Method Wet cure (water, burlap) or curing compound spray
Duration 7 days minimum; 28 days to reach full strength (4,000 psi)
Temp range 50 °F–90 °F

Source: ACI 308R-16

Delivery Estimate

Mixer trucks needed
1
Truck capacity
8–10 yd³
Estimated pour time
25 min

Most plants require a 1-yard minimum. Short-load fees ($50–$75/yd³ under minimum) may apply.

Frequently Asked Questions

  • How many bags of concrete do I need instead of a truck?

    One 80-lb bag covers 0.6 cubic feet. Divide your total cubic feet by 0.6. A 20 × 20 ft slab at 4 in deep is 133 cu ft ÷ 0.6 = 222 bags — at that scale, a truck is cheaper and the pour is far better quality.

  • What strength concrete do I need?

    Sidewalks and patios: 3,000 psi. Driveways: 3,500–4,000 psi. Garage floors and structural: 4,000+ psi. Ready-mix plants default to 3,000 psi; specify higher when ordering.

  • Do I need a permit for a concrete slab?

    In most U.S. jurisdictions, slabs over 200 sq ft or any slab attached to a structure require a building permit. Detached patios under 200 sq ft often do not. Check your local building department — the permit protects you from setback and drainage violations.

  • How long before I can drive on a new driveway?

    Light foot traffic: 24–48 hours. Vehicles: 7 days minimum for passenger cars, 28 days for heavy trucks. Concrete reaches 70% of its rated strength by day 7 and full strength by day 28.