Math Calculator
Circle Calculator
Calculate circle area, circumference, and diameter from radius.
⚠️ Please enter a valid positive radius.
Circle Results
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Calculator guide
How this calculator works
How to use this calculator
Enter the circle radius. The calculator returns the area, circumference, and diameter.
Formula used
Area = πr². Circumference = 2πr. Diameter = 2r.
Example calculation
If the radius is 5, the area is about 78.5398, the circumference is about 31.4159, and the diameter is 10.
What the result means
The area measures the space inside the circle. Circumference is the distance around the circle. Diameter is the distance across the circle through the center.
Frequently asked questions
What is radius?
Radius is the distance from the center of the circle to its edge.
What is diameter?
Diameter is twice the radius.
What units are used?
Use any unit for radius. Area is in square units, while circumference and diameter are in the same length unit.