Circle Diagram Depicting Each Measurement and Formula
Here is a brief, color-coded description of each of the four common circle measurements.
All of the area within the boundary of the circle, expressed as a square of the unit of measurement (square mm, square feet, etc.). The area can be found by multiplying PI (3.14159) times the radius times the radius again.
The distance around the outward boundary of a circle, expressed as a linear unit of measurement (millimeters, inches, etc.). The circumference can be found by multiplying PI (3.14159) times the diameter.
The length of a straight line that intersects the center point of the circle and reaches to each side of the boundary. Diameter can be found by multiplying the radius by two, or by dividing the circumference by PI (3.14159).
The length of a straight line drawn from the circle boundary to the center point of the circle. The radius can be found by dividing the diameter by two, or by finding the square root of the quotient resulting from dividing the area by PI (3.14159).
Note that the formulas used for finding each measurement will be listed in the calculator results.