Formula
Area uses the radius squared. Circumference uses the diameter's path:
Area = π × radius²
Circumference is 2 × π × radius. A sphere's surface is a different page.
Assumptions
- The radius is a straight line from the center to the edge.
- π is the standard circle constant.
Worked example
A radius of 7 has area 153.94.
Input definitions
- Radius
- The distance from the center to the edge.
Limitations
Area and circumference are rounded to two decimal places.
Questions
I know the diameter. What do I enter?
Enter half of the diameter as the radius.
Is the circumference the perimeter?
Yes. For a circle that distance is called the circumference.