How to Measure the Circumference of a Circle

Circumference is the distance around a circle. The steps for calculating circumference can be used to solve real life problems. For example, a jogger interested in knowing the distance around a circular path can easily estimate its circumference.

Things You'll Need

• Paper
• Pencil
• Calculator (optional)

Instructions

1. Measure diameter. The diameter of a circle is the distance across a circle, through its center. It can be visualized as a straight line cutting the circle in half. For large circles like running paths, the diameter can be estimated.

2. Consider radius. Radius is the distance from the center of a circle to any point on the circle. The radius of a circle is half its diameter. When diameter is too large to determine, estimate the radius. Then use simple math and multiply the radius by 2.

3. Grasp pi. Pi is the ratio of the circumference of a circle to its diameter. Pi is called a constant in math. It is a number that does not change, no matter the size of the circle. The value of pi is usually rounded to 3.14.

4. Calculate circumference. Use simple math to multiply the diameter of the circle by pi. If a jogger estimated diameter of a circular path as 200 meters across, then circumference would be 200 times 3.14 or 628 meters.

5. Verify units of measurement. The units for circumference are the same as the units for diameter. If diameter is measured in meters, report circumference in meters.

Tips & Warnings

• Use math to convert the units of measurement into the largest practical or logical measure. For example, report circumference of a circular jogging path in yards, miles or meters, not feet.

Resources

• Find more information on circumference of a circle and other math concepts.