Square Footage of a Circle Calculator
Created by: Daniel Hayes
Last updated:
To find the square footage of a circle, multiply pi (3.14159) by the radius squared, with the radius in feet. A circle 10 feet across has a 5 ft radius, so its area is 3.14159 × 25 = 78.54 sq ft. Enter the radius, diameter or circumference below, or look up common sizes in the charts.
Square Footage of a Circle Calculator
MathEnter the radius, diameter or circumference to get the area in square feet (π × r²)
What measurement do you know?
Square footage of a circle chart
Area in square feet for circles measured across the middle (diameter). Area = 0.7854 × diameter².
| Diameter | Radius | Square feet | Circumference |
|---|---|---|---|
| 1 ft | 0.5 ft | 0.79 | 3.14 ft |
| 2 ft | 1 ft | 3.14 | 6.28 ft |
| 3 ft | 1.5 ft | 7.07 | 9.42 ft |
| 4 ft | 2 ft | 12.57 | 12.57 ft |
| 5 ft | 2.5 ft | 19.63 | 15.71 ft |
| 6 ft | 3 ft | 28.27 | 18.85 ft |
| 8 ft | 4 ft | 50.27 | 25.13 ft |
| 10 ft | 5 ft | 78.54 | 31.42 ft |
| 12 ft | 6 ft | 113.10 | 37.70 ft |
| 14 ft | 7 ft | 153.94 | 43.98 ft |
| 15 ft | 7.5 ft | 176.71 | 47.12 ft |
| 16 ft | 8 ft | 201.06 | 50.27 ft |
| 18 ft | 9 ft | 254.47 | 56.55 ft |
| 20 ft | 10 ft | 314.16 | 62.83 ft |
| 24 ft | 12 ft | 452.39 | 75.40 ft |
| 25 ft | 12.5 ft | 490.87 | 78.54 ft |
| 30 ft | 15 ft | 706.86 | 94.25 ft |
| 36 ft | 18 ft | 1,017.88 | 113.10 ft |
| 40 ft | 20 ft | 1,256.64 | 125.66 ft |
| 50 ft | 25 ft | 1,963.50 | 157.08 ft |
| 60 ft | 30 ft | 2,827.43 | 188.50 ft |
| 75 ft | 37.5 ft | 4,417.86 | 235.62 ft |
| 100 ft | 50 ft | 7,853.98 | 314.16 ft |
Circles measured in inches
For round tables, rugs, tabletops, stepping stones and pipes.
| Diameter | Square inches | Square feet |
|---|---|---|
| 6 in | 28.3 | 0.20 |
| 8 in | 50.3 | 0.35 |
| 10 in | 78.5 | 0.55 |
| 12 in | 113.1 | 0.79 |
| 14 in | 153.9 | 1.07 |
| 16 in | 201.1 | 1.40 |
| 18 in | 254.5 | 1.77 |
| 20 in | 314.2 | 2.18 |
| 24 in | 452.4 | 3.14 |
| 30 in | 706.9 | 4.91 |
| 36 in | 1,017.9 | 7.07 |
| 42 in | 1,385.4 | 9.62 |
| 48 in | 1,809.6 | 12.57 |
| 54 in | 2,290.2 | 15.90 |
| 60 in | 2,827.4 | 19.63 |
| 72 in | 4,071.5 | 28.27 |
Circumference to square feet
| Circumference | Diameter | Square feet |
|---|---|---|
| 10 ft | 3.18 ft | 7.96 |
| 20 ft | 6.37 ft | 31.83 |
| 25 ft | 7.96 ft | 49.74 |
| 30 ft | 9.55 ft | 71.62 |
| 40 ft | 12.73 ft | 127.32 |
| 50 ft | 15.92 ft | 198.94 |
| 60 ft | 19.10 ft | 286.48 |
| 75 ft | 23.87 ft | 447.62 |
| 100 ft | 31.83 ft | 795.77 |
| 150 ft | 47.75 ft | 1,790.49 |
| 200 ft | 63.66 ft | 3,183.10 |
Square footage of a circle formula
From the radius: Area = π × r²
From the diameter: Area = π × d² ÷ 4 ≈ 0.7854 × d²
From the circumference: Area = C² ÷ (4π) ≈ C² ÷ 12.566
Measure in feet to get square feet. If you measured in inches, divide the area in square inches by 144. If you measured in meters, multiply square meters by 10.764.
Worked examples
Round patio, 16 ft across
Radius = 16 ÷ 2 = 8 ft. Area = 3.14159 × 8² = 3.14159 × 64 = 201.06 sq ft. Pavers and stone are usually ordered with 10% extra for the curved edge cuts, so plan for about 221 sq ft.
Above-ground pool, 24 ft diameter
Radius = 12 ft. Area = 3.14159 × 144 = 452.39 sq ft. That is the footprint to level and the size of the ground cloth or pad.
Circular flower bed measured around the edge
The edging is 30 ft long. Area = 30² ÷ 12.566 = 900 ÷ 12.566 = 71.62 sq ft. At 3 inches deep, mulch for that bed is 71.62 × 0.25 ÷ 27 = 0.66 cubic yards.
Frequently Asked Questions
How do you calculate the square footage of a circle?
Multiply pi (3.14159) by the radius squared: Area = π × r². Measure the radius in feet and the answer is in square feet. For example, a circle with a 10 ft radius is 3.14159 × 10 × 10 = 314.16 sq ft.
How do I find the square feet of a circle from the diameter?
Divide the diameter by 2 to get the radius, then use π × r². Or use Area = π × d² ÷ 4 directly, which works out to about 0.7854 × diameter². A 20 ft diameter circle is 0.7854 × 400 = 314.16 sq ft.
How do I find the square feet of a circle from the circumference?
Square the circumference and divide by 4π (about 12.566): Area = C² ÷ (4π). A circle measured at 60 ft around is 3,600 ÷ 12.566 = 286.48 sq ft.
How many square feet is a 12 foot circle?
A circle 12 feet across (diameter) is 113.10 sq ft. If 12 feet is the radius, the circle is 24 feet across and covers 452.39 sq ft, so check which measurement you have.
My measurements are in inches. How do I get square feet?
Convert the diameter or radius to feet first by dividing by 12, then use the formula. Or calculate the area in square inches and divide by 144. A 36 inch round table is 3 ft across, so its top is 0.7854 × 9 = 7.07 sq ft.
How do I measure a large circle like a patio or pool?
Measure straight across the widest point, through the center, to get the diameter. If you cannot reach across, run a tape around the outside edge to get the circumference and use the circumference formula instead.
How do I find the area of a half circle or quarter circle?
Find the full circle area, then multiply by 0.5 for a half circle or 0.25 for a quarter circle. A half circle with a 10 ft radius is 314.16 × 0.5 = 157.08 sq ft.
Sources and References
- NIST: Unit conversion. Area conversion factors, including 1 square meter = 10.7639 square feet.
- NIST Special Publication 811, Guide for the Use of the International System of Units