When to use this calculator
Recover a circle’s radius from its circumference. Circumference means distance around the circular edge.
Explore the circle & ellipse calculators for other questions in this topic. For a related calculation, use the Circle Segment Area Calculator: Calculate the smaller circular segment cut off by a chord.
PUTTING IT INTO PRACTICE
Circle Radius From Circumference: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Circumference | 31.415927 |
| Result | 5 units |
- Check the input labels and enter the example values above.
- Apply the relationship: Radius = circumference/(2π).
- The result is 5 units, rounded for display.
How to interpret your result
Circumference means distance around the circular edge.
Distinguish radius from diameter before entering measurements. Arc length follows the curve, while chord length runs straight between endpoints. Ring-shaped areas subtract the inner circle from the outer one.
Frequently asked questions
How is chord length different from arc length?
A chord is a straight line between two points on the circle. An arc follows the circular boundary between those points.
When is the circle radius from circumference calculator useful?
Recover a circle’s radius from its circumference. Circumference means distance around the circular edge.
How do I use the circle radius from circumference calculator?
Enter circumference. The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Radius = circumference/(2π).
What should I check before using the result?
Circumference means distance around the circular edge.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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