Circumference to Diameter Calculator
Find a circle's diameter from its circumference (or from its radius or area).
Change the values and press Calculate to work out your own figures.
Enter any one of the radius, diameter, circumference or area.
Show the working
- r = C ÷ 2π
- d = 2r, C = 2πr, A = πr²
- Diameter = 3.183098862 in
How to use it
Enter any one of the radius, diameter, circumference or area.
Enter the measurements (decimals, fractions such as 3/4, or mixed numbers such as 1 1/2) and, if you like, their unit; the answer is then also given in other units. Show the working gives the formula.
Key facts
d = C ÷ π
Measuring a tree or pipe
Wrap a tape around it and divide by π: a 100 cm girth is a diameter of 31.83 cm.
Questions
What diameter has a circumference of 10?
10 ÷ π ≈ 3.183098862.
Why divide by π?
Because C = π d.
Formulas
d = C ÷ π
Sources
Limitations
- All measurements in one calculation use the same unit; the answer is also given in other units.
- Measurements up to 10¹⁵.