30×40 Concrete Slab Cost
A 30×40 slab covers 1,200 square feet. Here's the concrete, bags and cost for 2026 — a common size for a shop / pole barn.
Concrete (4", waste in)
16.3 yd³
734 × 80 lb bags
Materials (ready-mix)
$2,037 – $3,096
delivered, 4" slab
Installed by a pro
$6,600 – $14,400
4" slab, national average
30×40 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
$6,600 – $14,400
1,200 sq ft · 16.3 yd³ concrete
Bags of concrete needed (rounded up)
734
80 lb
978
60 lb
1,174
50 lb
1,467
40 lb
- Ready-mix (delivered)
- $2,037 – $3,096
- Bagged mix (80 lb, DIY)
- $4,037 – $6,606
- Installed by a pro
- $6,600 – $14,400
Estimate only — not a quote. Bag counts are rounded up and include a 10% waste allowance.
30×40 slab cost by thickness
| Thickness | Concrete | 80 lb bags | Ready-mix | Installed |
|---|---|---|---|---|
| 4" | 16.3 yd³ | 734 | $2,037 – $3,096 | $6,600 – $14,400 |
| 5" | 20.37 yd³ | 917 | $2,546 – $3,870 | $7,500 – $15,300 |
| 6" | 24.44 yd³ | 1,100 | $3,056 – $4,644 | $8,400 – $16,200 |
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.
30×40 concrete slab: what to expect
A 30×40 slab covers 1,200 square feet. At the standard 4" thickness it takes about 16.3 cubic yards of concrete once you allow 10% for waste, which is roughly 734 × 80 lb bags if you mix by hand. Stepping up to 6" — sensible if it'll carry a vehicle — raises that to about 24.44 cubic yards.
Budget around $6,600 – $14,400 to have a 4" slab this size poured and finished by a contractor, or roughly $2,037 – $3,096 in ready-mix if you're doing the labor yourself. On top of the concrete you'll need about 17.04 yd³ of gravel base and 83 sticks of rebar.
Compare nearby sizes
Planning something bigger or smaller? Jump straight to the cost for a nearby size.
| Size | Concrete (4") | 80 lb bags | Installed cost |
|---|---|---|---|
| 30×30 | 12.22 yd³ | 550 | $4,950 – $10,800 |
| 24×40 | 13.04 yd³ | 587 | $5,280 – $11,520 |
| 1,000 sq ft | 13.58 yd³ | 612 | $5,500 – $12,000 |
| 30×50 | 20.37 yd³ | 917 | $8,250 – $18,000 |
| 1,500 sq ft | 20.37 yd³ | 917 | $8,250 – $18,000 |
| 40×40 | 21.73 yd³ | 978 | $8,800 – $19,200 |
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: