Circle Square Foot Calculator
Calculate the square footage of a circle from radius or diameter and convert the result to square meters, yards, inches, and acres.
Circle Square Footage Calculator
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Circle Square Footage Formula
The circle square footage formula is Area = π × r², where r is the radius in feet and π ≈ 3.14159. If you know the diameter instead, divide it by 2 to get the radius first.
A circular patio with a 10-foot diameter has a radius of 5 ft, giving an area of 3.14159 × 25 = 78.54 sq ft. This calculator uses a high-precision pi constant for maximum accuracy on large circular areas such as pools, roundabouts, and crop circles.
Unit Support
Enter the radius or diameter in feet, inches, meters, or centimeters. The calculator automatically converts your input to feet before applying the formula, then displays results in sq ft, sq meters, sq yards, sq inches, and acres.
How to Calculate Circle Square Footage
Follow these steps to find the square footage of any circular area:
- Measure the radius or diameter: Use a tape measure across the widest point of the circle. Half that measurement is the radius.
- Select your unit: Choose feet, inches, meters, or centimeters in the unit toggle above the calculator.
- Enter your value: Type the radius (or switch to diameter mode) into the input field.
- Read the result: The calculator instantly shows square footage, square meters, square yards, and acres.
Common Circular Area Examples
| Circular Area | Diameter | Square Feet |
|---|---|---|
| Round dining table | 5 ft | 19.63 sq ft |
| Round hot tub | 7 ft | 38.48 sq ft |
| Circular patio | 12 ft | 113.10 sq ft |
| Above-ground pool | 24 ft | 452.39 sq ft |
| Circular driveway | 40 ft | 1,256.64 sq ft |
All Square Foot Calculators
Choose a specialized calculator for your specific project type.
Frequently Asked Questions
Area = π × radius². Multiply pi (3.14159) by the radius squared. For a circle with a radius of 6 feet, the area is 3.14159 × 36 = 113.10 sq ft.
Divide the diameter by 2 to get the radius, then use Area = π × r². Or switch the calculator to "Diameter" mode and enter directly.
Yes. Calculate the full circle area using π × r², then divide by 2. A semicircle with a 10-foot radius has an area of (π × 100) ÷ 2 = 157.08 sq ft.
A 15-foot diameter circle (radius = 7.5 ft) has an area of π × 7.5² = 176.71 sq ft (16.42 sq meters).
You can enter dimensions in feet, inches, meters, or centimeters. The result is shown in sq ft, sq meters, sq yards, sq inches, and acres.
Calculate the outer circle area and the inner circle area separately, then subtract. For a ring with an outer radius of 8 ft and inner radius of 5 ft: (π × 64) − (π × 25) = 201.06 − 78.54 = 122.52 sq ft.