Circle Calculator
Radius, diameter, circumference, and area.
Radius
5
Diameter
10
Circumference
31.4159
Area
78.5398
Circumference = 2πr. Area = πr². Diameter = 2r.
About
Type any one value (radius, diameter, circumference, or area) and the tool computes the other three. Pi is taken to 16 decimal places, more than enough for anything practical.
How to use
- Pick which value you have.
- Enter the value.
- Read the others.
FAQ
Why does NASA only use 15 digits of pi?+
JPL has said publicly that 15 decimal places of pi is enough to compute the circumference of a 25-billion-mile circle to within an inch. Anything more is wasted precision.