Circle Diameter From Circumference Calculator

Work out circle diameter from circumference instantly with clear inputs, formula shown and shareable results.

About Circle Diameter From Circumference Calculator

Because C = πd, dividing a measured circumference by π recovers the diameter — the standard trick for sizing a pipe or tree trunk from a tape measurement around it.

Formulas

Diameter

d = C / π, r = C / (2π)

Area from circumference

A = C² / (4π)

Worked example

With the default values below, Circle Diameter From Circumference Calculator returns Diameter of 10.0000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Circumferenceminimum 0: 31.415927
Number of circlesminimum 1: 1

Results

Diameter: 10.0000
Radius: 5.0000
Area: 78.5398
Combined area: 78.5398

Step by step

1Values used
2Diameter
3Area from circumference
4Diameter= 10.0000
5Radius= 5.0000
6Area= 78.5398
7Combined area= 78.5398

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

A circumference of 31.415927 gives what diameter?

31.415927 / π = 10 exactly, so the radius is 5.

Is this how tree diameter is measured?

Yes. Foresters measure girth at breast height and divide by π to get diameter.