How Much Concrete for a 10x40 Slab?
How much concrete for a 10x40 slab depends on thickness. The slab covers 10 × 40 = 400 square feet, and at 4 inches thick that is about 4.94 cubic yards, or 5.43 yards with a 10 percent allowance. Mixed from bags, it is roughly 223 bags of 80 lb mix.
Concrete calculator →The math for a 10x40 slab
- Area: 10 ft × 40 ft = 400 sq ft.
- Thickness in feet: 4 in ÷ 12 = 0.333 ft.
- Volume: 400 × 0.333 = 133.3 cubic feet.
- Cubic yards: 133.3 ÷ 27 = 4.94 yd³.
- With 10% extra: 5.43 yd³.
The concrete calculator runs the same steps for any size and thickness.
Related: How Much Concrete for a 10x40 Driveway?
Concrete for a 10x40 slab by thickness
| Thickness | Cubic feet | Cubic yards | Yards +10% | 80 lb bags | 60 lb bags |
|---|---|---|---|---|---|
| 4 in | 133.3 | 4.94 | 5.43 | 223 | 297 |
| 5 in | 166.7 | 6.17 | 6.79 | 278 | 371 |
| 6 in | 200.0 | 7.41 | 8.15 | 334 | 445 |
Bag counts assume about 0.60 cubic feet per 80 lb bag and 0.45 per 60 lb bag, rounded up.
How thick to pour it
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 Gravel for a 10x40 Driveway?
Ordering ready-mix
Ready-mix is priced and batched by the cubic yard (27 cubic feet). Plants commonly add a small-load fee when an order is under a set minimum, so ask about it when you call. Ordering a little extra costs far less than a second truck.
Base and forms
Uneven ground is the main reason pours run short. Every half inch of extra depth across the slab adds concrete you did not plan for. Screed the base flat, check it with a string line and set the forms to finished height before the truck arrives.
Joints, mesh and rebar
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 12 feet apart control where cracks form.
Questions people ask
How many yards of concrete for a 10x40 slab at 4 inches?
About 4.94 cubic yards, or 5.43 with 10 percent extra.
How many yards for a 10x40 slab at 6 inches?
About 7.41 cubic yards.
How many 80 lb bags for a 10x40 slab?
About 223 bags at 4 inches thick, before any waste allowance.
How many square feet is a 10x40 slab?
400 square feet.
How many 80 lb bags make a cubic yard?
About 45. Each 80 lb bag yields roughly 0.6 cubic feet, and a cubic yard is 27 cubic feet.
When is bagged concrete practical?
Usually for jobs under about a cubic yard. Beyond that, mixing dozens of bags by hand gets slow and batches may not blend well.
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 10x35 Slab?
- How Much Concrete for a 10x36 Slab?
As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.