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Short answer
Halve the diameter to get the radius, then use A = πr² in feet. A 10 ft diameter circle is π × 5² = 78.54 sq ft. Divide square inches by 144 to convert to square feet.
1. Steps
- 1Measure the diameter across the middle of the circle.
- 2Halve it to get the radius.
- 3Convert the radius to feet.
- 4Calculate A = πr².
2. Examples
| Item | Radius | Area |
|---|---|---|
| 10 ft diameter patio | r = 5 ft | π × 5² = 78.54 sq ft |
| 36 in round table | r = 18 in | π × 18² = 1,017.88 sq in ÷ 144 = 7.07 sq ft |
| 2 m diameter circle | r = 1 m | π × 1² = 3.14 m² × 10.764 = 33.82 sq ft |
| 20 ft diameter pool | r = 10 ft | π × 10² = 314.16 sq ft |
3. Converting units
- Square inches to square feet: divide by 144.
- Square metres to square feet: multiply by 10.764.
- Square yards to square feet: multiply by 9.
4. Planning materials
Multiply the area by the price per square foot, and ask your supplier how much extra to buy for cuts and waste.
5. Frequently asked questions
How do I calculate the square feet of a circle?expand_more
Find the radius in feet and use A = πr².
How many square feet is a 10 ft circle?expand_more
A circle with a 10 ft diameter is 78.54 sq ft.
How do I convert square inches to square feet?expand_more
Divide by 144.
Should I measure the diameter or radius?expand_more
Either. The diameter is easier to measure; halve it for the radius.