How Much Concrete for a 6x30 Slab?
A 6 by 30 foot slab is 180 square feet. How much concrete for a 6x30 slab at the common 4-inch thickness: about 2.22 cubic yards. Most people order 2.50 yards to cover waste and an uneven base.
Concrete calculator →The math for a 6x30 slab
- Area: 6 ft × 30 ft = 180 sq ft.
- Thickness in feet: 4 in ÷ 12 = 0.333 ft.
- Volume: 180 × 0.333 = 60.0 cubic feet.
- Cubic yards: 60.0 ÷ 27 = 2.22 yd³.
- With 10% extra: 2.44 yd³.
The concrete calculator runs the same steps for any size and thickness.
Related: How Much Concrete for a 6x30 Sidewalk?
Concrete for a 6x30 slab by thickness
| Thickness | Cubic feet | Cubic yards | Yards +10% | 80 lb bags | 60 lb bags |
|---|---|---|---|---|---|
| 4 in | 60.0 | 2.22 | 2.44 | 100 | 134 |
| 5 in | 75.0 | 2.78 | 3.06 | 125 | 167 |
| 6 in | 90.0 | 3.33 | 3.67 | 150 | 200 |
Bag counts assume about 0.60 cubic feet per 80 lb bag and 0.45 per 60 lb bag, rounded up.
Choosing the thickness
Four inches is the usual thickness for patios, walks and shed floors. Slabs that carry cars or a heavy hot tub are often poured at 5 to 6 inches, and edges are sometimes thickened where loads concentrate.
Related: How Much Pea Gravel for a 6x30 Walkway?
Truck or bags?
A cubic yard of concrete is 27 cubic feet and weighs roughly 4,000 pounds. Most ready-mix trucks carry up to about 9 to 10 yards, though local trucks and rules vary. If your total is under a yard or two, bagged mix or a short-load supplier may be cheaper.
Getting the ground ready
Under the slab, most residential pours sit on about 4 inches of compacted gravel. The base spreads the load, drains water away and keeps the slab from cracking as the soil freezes and thaws. Compact the base in thin lifts, and dampen it just before the pour so it does not pull water out of the mix.
Joints and reinforcement
Reinforcement does not stop cracks, but it holds them tight. Wire mesh or rebar set mid-depth on chairs is common for a slab that carries vehicles; fiber-reinforced mix is an option for light-duty slabs. Joints about 10 feet apart control where cracks form.
Questions people ask
How many yards of concrete for a 6x30 slab at 4 inches?
About 2.22 cubic yards, or 2.44 with 10 percent extra.
How many yards for a 6x30 slab at 6 inches?
About 3.33 cubic yards.
How many 80 lb bags for a 6x30 slab?
About 100 bags at 4 inches thick, before any waste allowance.
How many square feet is a 6x30 slab?
180 square feet.
Should I add extra for waste?
Yes. Adding 5 to 10 percent covers uneven base, spillage and form bulges.
How thick should the base under the slab be?
About 4 inches of compacted gravel is common for residential slabs, more on soft or poorly drained soil.
Related guides
- How Much Area Does a Yard of Concrete Cover?
- How Many Bags of Concrete in a Yard? 40, 60, 80 lb
- Gravel Base Under a Concrete Slab: Depth and Tons
- How Many Yards in a Concrete Truck? Mixer Sizes
- Concrete Short Load Fee: What It Is and How to Cut It
- 60 lb vs 80 lb Concrete Bags: Yield, Count, and Cost
- Rebar vs Wire Mesh in a Slab: Which One to Use
- Cost to Pour a Concrete Slab: Per Square Foot
- How Much Concrete for a 6x26 Slab?
- How Much Concrete for a 6x28 Slab?
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