Circumference to Diameter Calculator
Calculate diameter and radius from a circle’s circumference. Select an input length unit; results are in centimeters.
Formula
d = C/π; r = C/(2π); results in cm.
Circumference: 31.42 cm · Diameter ≈ 100×(31.42 cm × 0.01 m/cm)÷pi · Radius ≈ (10.00129662)÷2
How to use
- Enter the circumference.
- Choose its length unit.
- Read the diameter and radius in cm.
Examples
- A circumference of 1 m gives a diameter of about 31.830989 cm.
Frequently asked questions
Is circumference a straight-line distance?
No. It is the distance once around the circle.
Does the input need to be in cm?
No. Supported length units are converted by the shared unit system.
Is this the same as entering a radius?
No. This tool starts with a measured circumference and solves for diameter.
Sources
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