30×30 Concrete Slab Cost
A 30×30 slab covers 900 square feet. Here's the concrete, bags and cost for 2026 — a common size for a large garage / shop.
Concrete (4", waste in)
12.22 yd³
550 × 80 lb bags
Materials (ready-mix)
$1,528 – $2,322
delivered, 4" slab
Installed by a pro
$4,950 – $10,800
4" slab, national average
30×30 slab cost calculator
Adjust thickness, waste or region — the cost updates live.
Waste & region
Order extra for spillage & uneven subgrade. 10% is typical.
Installed cost estimate
$4,950 – $10,800
900 sq ft · 12.22 yd³ concrete
Bags of concrete needed (rounded up)
550
80 lb
734
60 lb
880
50 lb
1,100
40 lb
- Ready-mix (delivered)
- $1,528 – $2,322
- Bagged mix (80 lb, DIY)
- $3,025 – $4,950
- Installed by a pro
- $4,950 – $10,800
Estimate only — not a quote. Bag counts are rounded up and include a 10% waste allowance.
30×30 slab cost by thickness
| Thickness | Concrete | 80 lb bags | Ready-mix | Installed |
|---|---|---|---|---|
| 4" | 12.22 yd³ | 550 | $1,528 – $2,322 | $4,950 – $10,800 |
| 5" | 15.28 yd³ | 688 | $1,910 – $2,903 | $5,625 – $11,475 |
| 6" | 18.33 yd³ | 825 | $2,292 – $3,483 | $6,300 – $12,150 |
Includes a 10% waste allowance; bag counts rounded up. National US averages, January 2026.
You'll also need
Sized for this exact slab — tap any item to open its calculator with your measurements already filled in.
30×30 concrete slab: what to expect
A 30×30 slab covers 900 square feet. At the standard 4" thickness it takes about 12.22 cubic yards of concrete once you allow 10% for waste, which is roughly 550 × 80 lb bags if you mix by hand. Stepping up to 6" — sensible if it'll carry a vehicle — raises that to about 18.33 cubic yards.
Budget around $4,950 – $10,800 to have a 4" slab this size poured and finished by a contractor, or roughly $1,528 – $2,322 in ready-mix if you're doing the labor yourself. On top of the concrete you'll need about 12.78 yd³ of gravel base and 63 sticks of rebar.
Compare nearby sizes
Planning something bigger or smaller? Jump straight to the cost for a nearby size.
Volumes use standard bag yields and a 10% waste allowance; costs are national US averages that vary by region, mix and finish. See our methodology for exactly how each figure is worked out, or check the reference sources: