Circle Circumference Calculator
Calculate a circle’s circumference from radius or diameter, or find the radius from a circumference or area.
Your inputs
Results
Circumference
31.415927 m
- Radius
- 5 m
- Diameter
- 10 m
✓Exact calculation — rounded only for display
What this calculator does
Circumference is the distance around a circle — for wheels, tubes, trees and tracks.
Formula and method
Worked example
Calculated by this tool with its default inputs:
Inputs
- Length unit: Metres
- I know the: Radius
- Value: 5
Results
- Circumference: 31.415927 m
- Radius: 5 m
- Diameter: 10 m
How to read the results
Wrap a tape around a tree to find its diameter: d = C ÷ π.
Assumptions and limitations
- Use one length unit consistently; areas are in square units and volumes in cubic units of that length.
Quantities and costs are planning estimates. Add sensible allowances, and check with suppliers, carriers or professionals before buying, shipping or building.
Questions
What is π?
The ratio of a circle’s circumference to its diameter, about 3.14159.
Methodology and verification
- Result type
- Exact mathematical calculation (rounded only for display)
- Formula version
- 1.0
- Automated verification
- 4 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
- Editorial review
- Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.
Privacy
Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Inputs are added to a share link only if you choose to include them. Privacy policy