Concrete for a 16x40 Slab
Order 8.69 yd with 10% waste — or 356 × 80 lb bags / 475 × 60 lb bags.
By thickness
| Thickness | Cubic yards | +10% waste | 80 lb bags | Typical use |
|---|---|---|---|---|
| 4" | 7.90 | 8.69 | 356 | Patio, shed pad, walkway |
| 5" | 9.88 | 10.86 | 445 | Light vehicle traffic |
| 6" | 11.85 | 13.04 | 534 | Driveway, garage |
Bags or the truck?
For this 640 sq ft slab at 4": bags ≈ $2,314 (356 × 80 lb — that's 28,480 lb of mixing) vs ready-mix ≈ $1,225 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 16x40 slab?
A 16x40 slab at the standard 4-inch thickness needs 7.90 cubic yards of concrete — order 8.69 yards with a 10% waste margin. At 6 inches it needs 11.85 yards.
How many bags of concrete for a 16x40 slab?
At 4 inches thick: 356 bags of 80 lb concrete mix or 475 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 16x40 slab?
Ready-mix. Bags for this slab would cost about $2,314 in material and require mixing 28,480 lb by hand; a delivered order runs roughly $1,225 and arrives ready to pour.