How Much Concrete for an 8 Foot Round Slab?
A round pad 8 feet in diameter covers about 50.3 square feet. How much concrete for an 8 foot round slab at 4 inches: 0.62 cubic yards, or about 28 bags of 80 lb mix.
Concrete calculator →The circle math
- Radius: 8 ÷ 2 = 4 ft.
- Area: 3.1416 × 4 × 4 = 50.3 sq ft.
- Volume at 4 in: 50.3 × 0.333 = 16.8 cu ft.
- Yards: ÷ 27 = 0.62 yd³.
A round slab takes about 21 percent less concrete than a square of the same width (8x8 would need 0.79 yards at 4 inches).
Related: How Much Concrete for a 24 Foot Round Slab?
By thickness
| Thickness | Cubic feet | Cubic yards | Yards +10% | 80 lb bags | 60 lb bags |
|---|---|---|---|---|---|
| 4 in | 16.8 | 0.62 | 0.68 | 28 | 38 |
| 5 in | 20.9 | 0.78 | 0.85 | 35 | 47 |
| 6 in | 25.1 | 0.93 | 1.02 | 42 | 56 |
Forming a circle
Mark the circle with a stake and a string the length of the radius. Flexible form material such as hardboard strips or plastic forms bends to the curve; stake it closely, since curves push outward when the concrete goes in.
Related: How Much Concrete for a 12 Foot Round Slab?
Common uses and thickness
Round pads are popular for fire pit seating areas, grill stations, gazebos and tank bases. Four inches suits foot traffic and furniture; a gazebo, hot tub or tank needs a thicker slab and a well-compacted base, and a tank base may have engineering requirements.
Joints in a round slab
Cut control joints like pie slices from the center outward, with an optional ring joint for larger circles, so each panel stays a manageable size.
Questions people ask
How many yards of concrete for an 8 ft round slab?
About 0.62 cubic yards at 4 inches.
How many square feet is an 8 ft circle?
About 50.3 square feet.
How many 80 lb bags for an 8 ft round slab?
About 28 bags at 4 inches thick.
How do I find the area of a circle?
Multiply 3.1416 by the radius squared. The radius is half the diameter.
How much does a cubic yard of concrete weigh?
Roughly 4,000 pounds, or about 2 tons, for normal-weight concrete.
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
- Gravel for a Fire Pit Area: Best Types and Depth
- How Much Concrete for a 24 Foot Round Slab?
- How Much Concrete for a 6 Foot Round Slab?
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