Circumference/sərˈkʌmfərəns/ Definition 1 of 2Pro Tip 1/3Mathematical Context Circumference is often used in geometry and involves calculations. To find the circle's area, you first need its circumference. Pro Tip 2/3Measurements Involved When discussing circumference, expect to use units of length like meters or inches. What's the circumference of this field in meters? Pro Tip 3/3Circle Specifics Circumference is specific to round shapes; don't use it for squares or rectangles. The circumference, not the width, dictates how much fence we need.