Circumference Calculator
Find a circle's circumference from its radius, diameter 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
- d = 2r, C = 2πr, A = πr²
- Circumference = 62.83185307 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
C = 2πr = πd
π
π is the ratio of any circle's circumference to its diameter, 3.14159265…
Questions
What is the circumference of a circle of radius 10?
20π ≈ 62.83185307.
What is the circumference of a 1-meter wheel?
π ≈ 3.141592654 m.
Formulas
C = 2πr = πd
Sources
Limitations
- All measurements in one calculation use the same unit; the answer is also given in other units.
- Measurements up to 10¹⁵.