How Much Concrete for a 8x8 Slab?
A 8×8 ft slab covers 64 sq ft. At the standard 4-inch thickness it needs 0.79 cubic yards of concrete – about 40 bags of 80 lb mix including 10% extra. Adjust the thickness below for your project.
Cubic yards (with waste)0.87
Cubic feet23.5
80 lb bags (0.60 cu ft)40
60 lb bags (0.45 cu ft)53
40 lb bags (0.30 cu ft)79
Ready-mix cost$143
Concrete for a 8x8 slab by thickness
| Thickness | Cubic yards | Yards +10% | 80 lb bags | 60 lb bags | Ready-mix cost* |
|---|---|---|---|---|---|
| 4 in | 0.79 | 0.87 | 40 | 53 | $143 |
| 5 in | 0.99 | 1.09 | 49 | 66 | $179 |
| 6 in | 1.19 | 1.3 | 59 | 79 | $215 |
*At about $165 per cubic yard before delivery and short-load fees. Bag counts include 10% extra.
How it is calculated
8 ft × 8 ft × (4 in ÷ 12) = 21.3 cu ft
21.3 cu ft ÷ 27 = 0.79 cubic yards
80 lb bags = 21.3 × 1.10 ÷ 0.60 = 40
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 8x8 slab?
A 8x8 slab (64 sq ft) needs 0.79 cubic yards at 4 inches thick, 0.99 yd³ at 5 inches and 1.19 yd³ at 6 inches, before waste.
How many bags of concrete for a 8x8 slab?
At 4 inches thick with 10% extra, you need about 40 bags of 80 lb concrete mix or 53 bags of 60 lb mix.
Should I use bags or ready-mix for a 8x8 slab?
At under a cubic yard, bagged concrete is practical and usually cheaper than a ready-mix short-load fee.