How Much Concrete for a 24x30 Slab?
A 24×30 ft slab covers 720 sq ft. At the standard 4-inch thickness it needs 8.89 cubic yards of concrete – about 440 bags of 80 lb mix including 10% extra. Adjust the thickness below for your project.
Concrete for a 24x30 slab by thickness
| Thickness | Cubic yards | Yards +10% | 80 lb bags | 60 lb bags | Ready-mix cost* |
|---|---|---|---|---|---|
| 4 in | 8.89 | 9.78 | 440 | 587 | $1,613 |
| 5 in | 11.11 | 12.22 | 550 | 734 | $2,017 |
| 6 in | 13.33 | 14.67 | 661 | 881 | $2,420 |
*At about $165 per cubic yard before delivery and short-load fees. Bag counts include 10% extra.
How it is calculated
24 ft × 30 ft × (4 in ÷ 12) = 240 cu ft
240 cu ft ÷ 27 = 8.89 cubic yards
80 lb bags = 240 × 1.10 ÷ 0.60 = 440
Which thickness do you need?
- 4 inches – patios, walkways, shed floors and most residential garage floors.
- 5–6 inches – driveways, hot tub pads, and garages for heavier trucks or RVs.
- Add 4–6 inches of compacted gravel base underneath and use rebar or wire mesh for slabs larger than about 10×10 ft.
Frequently asked questions
How many yards of concrete for a 24x30 slab?
A 24x30 slab (720 sq ft) needs 8.89 cubic yards at 4 inches thick, 11.11 yd³ at 5 inches and 13.33 yd³ at 6 inches, before waste.
How many bags of concrete for a 24x30 slab?
At 4 inches thick with 10% extra, you need about 440 bags of 80 lb concrete mix or 587 bags of 60 lb mix.
Should I use bags or ready-mix for a 24x30 slab?
At 9.8 cubic yards, ready-mix delivery is usually faster and more consistent than mixing 440 bags by hand. Many suppliers charge a short-load fee under 3–4 yards.