Enter a circle’s radius to find its diameter, circumference and area. Everything runs in your browser — nothing you enter here is uploaded, stored, or logged.
Calculated locally in your browser — nothing is sent to our server.
Diameter
Circumference
Area
How This Calculation Works
Given the radius (r), the diameter is 2r, the circumference is 2πr, and the area is πr². This calculator uses JavaScript’s built-in, full-precision value of π rather than a rounded approximation like 3.14, so results are as accurate as floating-point arithmetic allows.
FAQ
Can I enter the diameter instead of the radius?
Not in this version — enter the radius (half the diameter). If you know the diameter, divide it by 2 first.
Is my data uploaded anywhere?
No. The calculation happens entirely in your browser using JavaScript.