Concrete planning tool
Concrete Circular Slab Calculator
Estimate the concrete volume for one solid circular slab using its diameter, uniform thickness, and an optional waste allowance.
Circular slab inputs
Enter the slab dimensions
Enter one solid circular slab with a uniform thickness.
Concrete required
Concrete volume for this circular slab
Concrete required
1.07yd³
- Circular area
- 78.54 ft²
- Volume before waste
- 0.97 yd³
- Waste allowance
- 0.10 yd³
- Including waste
- 1.07 yd³
Estimating packaged concrete? Use the Concrete Bag Calculator.
Live diagram
Circular slab visualization
Diagram shows relative proportions, not scale.
How it works
From circular dimensions to concrete volume
The calculator finds the area of the circular footprint, multiplies it by the uniform slab thickness, and adds your selected waste allowance.
Circular slab formula
Divide the diameter by two to find the radius, then use the circle area and uniform thickness to calculate volume.
Area = π × radius²
Volume = π × radius² × thickness
Required concrete = volume × (1 + waste percentage ÷ 100)
Worked example: 10 ft diameter × 4 in thick
This arithmetic example models a uniform circular slab and is not a thickness or structural recommendation.
- Circular area78.54 ft²
- Before waste0.97 yd³
- 10% waste0.10 yd³
- Concrete required1.07 yd³
Diameter and radius
Measure the full distance across the center of the circular slab and enter it as the diameter. The calculator divides that value by two to obtain the radius used in the formula.
Choosing a thickness
Enter the uniform thickness specified for your project. This calculator does not select a thickness or determine structural suitability.
Waste allowance
Waste is shown separately and added after the base slab volume. No universal allowance is assumed.
Cubic feet, cubic yards, and cubic meters
US results emphasize cubic yards. Metric results use cubic meters. Switching systems preserves the same physical slab and calculation precision.
Estimate limitations
This calculator models one solid, level circular slab with uniform thickness. It does not model rings, openings, multiple circles, irregular shapes, slopes, reinforcement, excavation, base material, labor, pricing, structural design, or code compliance.
Use project plans, local requirements, and qualified professional guidance where required.
Frequently asked questions
- How much concrete do I need for a circular slab?
- Multiply the circular area by the uniform thickness, then add the waste allowance appropriate for your project.
- How is circular concrete volume calculated?
- The calculator uses π × radius² for area, multiplies that area by thickness, and then applies your waste percentage.
- Should I measure diameter or radius?
- Measure and enter the diameter—the full distance across the circle through its center. The calculator derives the radius.
- Does thickness affect concrete quantity?
- Yes. For the same diameter, increasing the uniform thickness increases the required concrete volume proportionally.
- Does this include reinforcement?
- No. Reinforcement selection, spacing, and structural design are outside this material-volume estimate.
- Should I add waste?
- Use the allowance appropriate to your placement and project conditions; the calculator does not prescribe one.
- Can it calculate concrete bags?
- Use the Concrete Bag Calculator with this required volume and the product’s stated yield.
- Can it calculate circles with holes?
- No. V1 supports one solid circular slab. Rings, holes, cutouts, and multiple circular sections are not included.