Circle Calculator
Area, circumference, and diameter from the radius.
How it works
Area = π × r². Circumference = 2 × π × r.
FAQ
Is this calculator free?
Yes. No signup is needed and nothing you enter is stored.
Is the result exact?
Results are rounded for display. For financial, medical, or legal decisions, confirm with a professional.
Do my numbers leave my device?
No. The calculation runs in your browser.