Free Circle Area, Circumference, Diameter & Radius Calculator Online
Calculate circle area (A = πr²), circumference (C = 2πr), diameter, sector area, and arc length given any single known parameter. — 100% free online utility, zero sign-up, zero paywalls, and private client-side processing.
How It Works
Enter Any Dimension
Input known Radius, Diameter, Circumference, or Area.
Instant Solving
Computes all corresponding circle measurements.
Inspect Sector Option
Optionally enter central angle (θ) to compute sector slice area.
Frequently Asked Questions
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