# How to measure the circumference of a circle

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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.

Skill level:
Easy

### Things you need

• Paper
• Pencil
• Calculator (optional)

## Instructions

1. 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. 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. 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. 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. 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 and 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.

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