Concrete for a 30x30 Slab
Order 12.22 yd with 10% waste — or 500 × 80 lb bags / 667 × 60 lb bags.
By thickness
| Thickness | Cubic yards | +10% waste | 80 lb bags | Typical use |
|---|---|---|---|---|
| 4" | 11.11 | 12.22 | 500 | Patio, shed pad, walkway |
| 5" | 13.89 | 15.28 | 625 | Light vehicle traffic |
| 6" | 16.67 | 18.33 | 751 | Driveway, garage |
Bags or the truck?
For this 900 sq ft slab at 4": bags ≈ $3,250 (500 × 80 lb — that's 40,000 lb of mixing) vs ready-mix ≈ $1,722 delivered. The truck wins here. Prices are national ballparks — your local quote rules.
Adjust the numbers
Common questions
How much concrete do I need for a 30x30 slab?
A 30x30 slab at the standard 4-inch thickness needs 11.11 cubic yards of concrete — order 12.22 yards with a 10% waste margin. At 6 inches it needs 16.67 yards.
How many bags of concrete for a 30x30 slab?
At 4 inches thick: 500 bags of 80 lb concrete mix or 667 bags of 60 lb. At this volume, delivered ready-mix is usually cheaper and far less work than mixing bags.
Should I use bags or ready-mix for a 30x30 slab?
Ready-mix. Bags for this slab would cost about $3,250 in material and require mixing 40,000 lb by hand; a delivered order runs roughly $1,722 and arrives ready to pour.