Circle Calculator

Facts About the Circle

• A circle is a 2D shape made of all points that are the same distance from a fixed point called the center.
• The distance from the center to any point on the circle is called the radius (r).
• The distance across the circle through the center is the diameter (d).
• The diameter is always twice the radius.
• The line around a circle is called the circumference (C).

Angle & Arc Facts

• A circle contains 360 degrees.
• A semicircle is half a circle (180°).
• A quarter circle is 90°.
• An arc is a portion of the circle’s edge.
• A chord is a line segment connecting two points on a circle.
• The diameter is the longest chord in a circle.
• A tangent touches a circle at exactly one point.

Fun Trivia

• A circle has infinite lines of symmetry.
• A circle has no corners and no sides.
• The ratio of circumference to diameter is always π.
• Among all shapes with the same perimeter, the circle encloses the largest area.
• Circles appear everywhere in real life — wheels, coins, clocks, planets, bubbles, and ripples in water.

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