Calculate circle area, circumference, radius, and diameter. Enter any one value to calculate all other circle properties.
A = πr²
The area of a circle is pi times the radius squared. This represents the total space enclosed by the circle.
C = 2πr = πd
The circumference is the distance around the circle. It equals 2π times the radius or π times the diameter.
d = 2r
The diameter is the distance across the circle through its center. It is always twice the radius.
r = d/2
The radius is the distance from the center to any point on the circle. It is half the diameter.
Pi (π) is a mathematical constant approximately equal to 3.14159. It represents the ratio of a circle's circumference to its diameter, and this ratio is the same for all circles regardless of size.
Approximate Value
3.14159
Common Fraction
22/7
Type
Irrational
The center is the point equidistant from all points on the circle. All radii extend from this point.
A line segment connecting any two points on the circle. The diameter is the longest possible chord.
A portion of the circumference between two points. The entire circumference is a 360° arc.
A region bounded by two radii and an arc, like a slice of pie. Area = (θ/360°) × πr².
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