Radius from Circumference
Useful for tree trunks or pipes where the diameter cannot be measured directly. Divide the circumference by 2π (about 6.283).
Your numbers
Radius
15.915cm
Area
795.77cm²
Diameter
31.831cm
Formula
Radius = Circumference ÷ (2π)
A 100 cm circumference means a 15.9 cm radius. On trees, bark thickness inflates the result over the actual wood.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Circumference (cm)The distance once around a circle. | 100 | 0 and up |
Step by step
Quick reference table
Results when only Circumference (cm) changes and everything else stays put.
| Circumference (cm) | Radius (cm) | Area (cm²) | Diameter (cm) |
|---|---|---|---|
| 50 | 7.958 | 198.94 | 15.915 |
| 75 | 11.937 | 447.62 | 23.873 |
| 100 | 15.915 | 795.77 | 31.831 |
| 150 | 23.873 | 1,790.49 | 47.746 |
| 200 | 31.831 | 3,183.1 | 63.662 |
What each result means
| Result | At default values |
|---|---|
| Radius (cm)Centre to edge — half the diameter. | 15.915 |
| Area (cm²)The space a shape covers — length squared. | 795.77 |
| Diameter (cm)The longest line across a circle — twice the radius. | 31.831 |
Common mistakes
A 100 cm circumference means a 15.9 cm radius. On trees, bark thickness inflates the result over the actual wood.
Glossary
- Circumference
- The distance once around a circle.
- Radius
- Centre to edge — half the diameter.
- Area
- The space a shape covers — length squared.
- Diameter
- The longest line across a circle — twice the radius.
Frequently asked questions
QHow is Radius from Circumference calculated?
Radius = Circumference ÷ (2π) — Useful for tree trunks or pipes where the diameter cannot be measured directly. Divide the circumference by 2π (about 6.283).
QCan you walk through an example?
With Circumference 100cm, the answer is Radius 15.915cm.
QWhat do I need to enter?
Enter Circumference. The result recalculates as you type, and an empty box counts as zero.
QHow much does the answer move if I change a number?
Changing only Circumference (cm) moves the answer to Circumference (cm) 50 → Radius (cm) 7.958 and Circumference (cm) 200 → Radius (cm) 31.831. The table below lays out five steps.
QHow are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
QAnything to watch out for?
A 100 cm circumference means a 15.9 cm radius. On trees, bark thickness inflates the result over the actual wood.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.