Free · Plane geometry calculators 🔺

Circle Diameter and Radius Conversion

Calculate circle diameter and radius conversion with bidirectional inputs, compatible units and clear geometric assumptions.

  • Formula & worked example
  • Private in your browser
  • No signup
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

A diameter of 10 centimeters corresponds to a radius of 5 centimeters.

d = 2r

Worked example

Enter these known values and leave the other values blank.

Diameter (d)
10 cm
Radius (r)
5 cm

Assumptions and limitations

  • The radius is half the diameter of a Euclidean circle.
  • Both measurements use length units, with selected units converted before calculation.
  • The captured model includes a zero-size boundary.
  • Arithmetic uses 64 significant digits, with separate display rounding.

Common questions

Can I convert a radius back into a diameter?

Enter the known radius and clear the diameter. The inverse relation doubles the radius before applying the selected display unit.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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