Calculate circle area, circumference, and diameter
314.16
sq ft
62.83
ft
20.00
ft
Area
314.16
sq ft
Circumf.
62.83
ft
Diameter
20.00
ft
Area = π × r²The area enclosed by a circle, calculated as pi times the radius squared.
Where:
r= Radius of the circleπ= Pi, approximately 3.14159Circumference = 2 × π × rThe perimeter (distance around) the circle.
Where:
r= Radius of the circleπ= Pi, approximately 3.14159Diameter = 2 × rThe diameter is twice the radius, passing through the center of the circle.
Where:
r= Radius of the circleInputs
Result
Area = π × 10² = π × 100 = 314.16. Circumference = 2 × π × 10 = 62.83. Diameter = 2 × 10 = 20.00.
Inputs
Result
Area = π × 7² = π × 49 = 153.94. Circumference = 2 × π × 7 = 43.98. Diameter = 2 × 7 = 14.00.
Area of a circle = π × r², where r is the radius. For example, a circle with radius 5 has area = π × 5² = 78.54 square units. Alternatively, area = π × (d/2)² where d is the diameter.
Circumference = 2 × π × r, where r is the radius. For a circle with radius 10, circumference = 2 × π × 10 = 62.83 units. Alternatively, circumference = π × d where d is the diameter.
Diameter = 2 × radius. The diameter is twice the radius. If radius is 5, diameter is 10. The radius is half the diameter.
π (pi) is approximately 3.14159, but is often rounded to 3.14 for calculations. It represents the ratio of a circle's circumference to its diameter. For precise calculations, use π = 3.14159265359.
A circle is defined by its radius (distance from center to edge). All circle measurements can be calculated from the radius.
The area of a circle is π times the radius squared. The circumference is 2π times the radius.
The diameter is always twice the radius, and the circumference equals π times the diameter.
Last Updated: Feb 12, 2026
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