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Circular Area Calculator

Measuring a round bed, fire pit surround, or tree ring? Enter the diameter and depth to get the cubic yards of material required.

Dimensions

Common depths:

Add extra for waste and uneven ground

Example: 10 ft circle, 3 in deep

0.73cubic yards

19.63 cubic feet · 0.56 m³

Or in bags: 20 × 1 cu ft · 14 × 1.5 cu ft · 10 × 2 cu ft · 7 × 3 cu ft

Enter your own measurements above to replace this example.

Results are estimates; compaction and uneven ground can change how much you need. We recommend ordering 5–10% extra.

How to calculate cubic yards for a circle

Find the area with π × radius × radius (the radius is half the diameter), multiply by the depth in feet, and divide by 27. A round bed 10 feet across, covered 3 inches deep, is about 19.6 cubic feet, or 0.73 cubic yards.

Formula

Area (sq ft) = 3.1416 × radius (ft) × radius (ft)

Cubic yards = area × depth (ft) ÷ 27

1 cubic yard = 27 cubic feet (3 ft × 3 ft × 3 ft)

Worked example

10 ft circle, 3 in deep

  1. Find the area: π × 5 ft × 5 ft = 78.54 sq ft (the radius is half the diameter).
  2. Convert the depth to feet: 3 in ÷ 12 = 0.25 ft.
  3. Multiply by the depth: 78.54 sq ft × 0.25 ft = 19.63 cubic feet.
  4. Divide by 27: 19.63 ÷ 27 = 0.73 cubic yards.

Measuring a round area

Measure straight across the circle through its center at the widest point. That is the diameter; half of it is the radius. If the shape is not quite round, measure across it in two directions and use the average.

Rings around trees and fire pits

For a ring, work out the outer circle and subtract the inner circle the tree or fire pit sits in. Enter the inner diameter in the calculator and it does the subtraction. A ring 8 feet across around a 2-foot center covers about 47 square feet; at 3 inches deep that is about 0.44 cubic yards.

Cubic yards for round beds

Material needed to cover a circle of each diameter.

Diameter2 in3 in4 in
4 ft0.08 yd³0.12 yd³0.16 yd³
6 ft0.17 yd³0.26 yd³0.35 yd³
8 ft0.31 yd³0.47 yd³0.62 yd³
10 ft0.48 yd³0.73 yd³0.97 yd³
12 ft0.7 yd³1.05 yd³1.4 yd³
16 ft1.24 yd³1.86 yd³2.48 yd³
20 ft1.94 yd³2.91 yd³3.88 yd³

Frequently asked questions

How do I find the cubic feet of a circle?

Multiply π (3.1416) × radius × radius to get the area in square feet, then multiply by the depth in feet. A 10 ft circle 3 inches (0.25 ft) deep is 78.5 × 0.25 = 19.6 cubic feet.

What if I only know the circumference?

Divide the circumference by π (3.1416) to get the diameter. A circle 31.4 feet around is 10 feet across.

How many cubic feet are in a cubic yard?

27. Divide cubic feet by 27 to get cubic yards.

Order by the cubic yard

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