Concrete for a 14x20 Slab
Order 3.80 yd with 10% waste — or 156 × 80 lb bags / 208 × 60 lb bags.
By thickness
| Thickness | Cubic yards | +10% waste | 80 lb bags | Typical use |
|---|---|---|---|---|
| 4" | 3.46 | 3.80 | 156 | Patio, shed pad, walkway |
| 5" | 4.32 | 4.75 | 195 | Light vehicle traffic |
| 6" | 5.19 | 5.70 | 234 | Driveway, garage |
Bags or the truck?
For this 280 sq ft slab at 4": bags ≈ $1,014 (156 × 80 lb — that's 12,480 lb of mixing) vs ready-mix ≈ $611 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 14x20 slab?
A 14x20 slab at the standard 4-inch thickness needs 3.46 cubic yards of concrete — order 3.80 yards with a 10% waste margin. At 6 inches it needs 5.19 yards.
How many bags of concrete for a 14x20 slab?
At 4 inches thick: 156 bags of 80 lb concrete mix or 208 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 14x20 slab?
Ready-mix. Bags for this slab would cost about $1,014 in material and require mixing 12,480 lb by hand; a delivered order runs roughly $611 and arrives ready to pour.