Calculate radius, diameter, circumference, or area of a circle – enter any one value.
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Circle Diagram
About Circles
A circle is defined by its radius. From it, you can calculate the diameter (2R), circumference (2πR), and area (πR²).
Real-world Examples
- Pizza: The size of a pizza is usually measured by its diameter
- Wheels: The circumference determines how far a wheel travels in one rotation
- Clocks: Clock faces are circular, with the radius determining the size
Frequently Asked Questions
What units can I use?
You can use any consistent units (mm, cm, m, km, in, ft, yd, mi). The calculator will maintain the same units for all results.
What's the difference between circumference and diameter?
The diameter is the distance across the circle through its center, while the circumference is the distance around the circle.
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