Circle Radius from Circumference Calculator
Work backwards from the distance around a circle to its radius, diameter and area. Enter circumference to see radius, diameter and area when you…
8 of 8 free uses remaining today
Work backwards from the distance around a circle to its radius, diameter and area. Enter circumference to see radius, diameter and area when you calculate.
Worked example
Example calculated from the starting values. Enter your own values and press Calculate to get your result.
With the default inputs (circumference = 31.4), the results are: radius 4.997; diameter 9.995; area 78.460.
Quick reference: circumference vs result
Reference table based on the example values; it is not your calculation result.
| Circumference | Radius | Diameter | Area |
|---|---|---|---|
| 15.7 | 2.499 | 4.997 | 19.615 |
| 31.4 | 4.997 | 9.995 | 78.460 |
| 62.8 | 9.995 | 19.990 | 313.841 |
| 157 | 24.987 | 49.975 | 1,961.505 |
| 314 | 49.975 | 99.949 | 7,846.020 |
| 628 | 99.949 | 199.899 | 31,384.082 |
Frequently asked questions
What formula does this calculator use?
Radius = c ÷ (2 × pi); Diameter = c ÷ pi; Area = c^2 ÷ (4 × pi). Variables: c = circumference.
What do I need to enter?
You need circumference. Results update as you type.
What is an example result?
With the default inputs (circumference = 31.4), the results are: radius 4.997; diameter 9.995; area 78.460.
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