Circumference Calculator
Calculate the circumference of a circle from its radius, with the diameter shown as well.
- Diameter
- 10
Formula: C = 2 × π × r
About Circumference Calculator
Circumference Calculator is a free online calculator that gives you an instant, accurate result as you type. Calculate the circumference of a circle from its radius, with the diameter shown as well.
The calculation uses the standard formula C = 2 × π × r and updates live with every change to the inputs. Everything runs client-side in your browser — fast, private, and free to use as often as you like.
The ratio of any circle’s circumference to its diameter is always π, approximately 3.14159.
Frequently Asked Questions
Is Circumference Calculator free to use?
Yes. Circumference Calculator is completely free, with no sign-up, no downloads, and no usage limits. You can use it as many times as you like on any device with a web browser.
How accurate is this calculator?
The calculator applies the standard formula (C = 2 × π × r) with full floating-point precision and rounds only the displayed result. For most practical purposes the results are exact.
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