The circumference of a circle equals the distance around the circle. To calculate the circumference of a circle in feet, you need to know either the radius or the diameter of the circle in feet. The mathematical relationship between the circumference and the diameter is known as pi, which is approximated at 3.14. If you have the measurement of the radius or diameter in a different unit of measure, you must first convert it to feet. For example, to convert a measurement in inches to feet, divide by 12.

Measure the radius of the circle in feet.

Multiply the radius of the circle by 2 to find the diameter of the circle in feet. For example, if the radius of the circle equals 3.8 feet, multiply 3.8 by 2 to find the diameter equals 7.6 feet.

Multiply the diameter of the circle by 3.14 to find the circumference of the circle in feet. In this example, multiply 7.6 feet by 3.14 to find the circumference of the circle to be 23.864 feet.