Circle Square Footage Calculator
Enter the radius (or half the diameter) of any circle. We'll calculate the area in square feet using the formula π × r².
Last updated:Tip: If you only have the diameter, divide by 2 to get the radius.
L-shape = two rectangles sharing a corner.
Add one row per rectangle and we'll sum them.
Circle Square Footage Formula
The area of a circle is π × radius². Using π ≈ 3.14159:
- Radius = 5 ft → π × 5² = 78.54 sq ft
- Radius = 10 ft → π × 10² = 314.16 sq ft
- Radius = 15 ft → π × 15² = 706.86 sq ft
If you only have the diameter, divide it by 2 first. A 20-ft diameter pool has a 10-ft radius and therefore an area of 314.16 sq ft.
Common Uses for a Circle Square Footage Calculator
Round pools, garden beds, silos, trampolines, and patios are the most common reasons to calculate circular area. For a round above-ground pool, measure the inner diameter at the water line, divide by 2, and enter the radius.
Construction workers use this for circular concrete pads, landscaping uses it for round sod cuts, and event planners use it for circular tent layouts. Our pool square footage calculator uses this exact formula.
Half-Circle and Quarter-Circle Areas
A semicircle (half-circle) is exactly half the area of a full circle: (π × r²) / 2. A quarter-circle is one-quarter: (π × r²) / 4.
Calculate the full circle area in the tool above, then divide.
Frequently Asked Questions
What is the square footage of a 10-foot radius circle?
π × 10² = 314.16 sq ft (approximately 29.19 sq m).
How do I calculate area from a diameter?
Divide the diameter by 2 to get the radius, then use π × r². For a 24-foot diameter, the radius is 12 ft and the area is 452.39 sq ft.
What's the area of a 20-foot round pool?
If "20 feet" refers to the diameter (most common), radius = 10 ft and area = 314.16 sq ft. If it's the radius, area = 1,256.64 sq ft.
Does this work for circular patios?
Yes. Measure the radius from center to edge, enter it, and add the optional waste factor if you're ordering pavers or concrete.