How to Calculate Circumference Using Diameter
- 1). Retrieve the mathematical constant pi with the desired accuracy (see Resources); the pi value rounded to the fourth decimal point, 3.1416, is sufficient for most calculations.
- 2). Measure or obtain elsewhere the diameter of the circle.
- 3). Multiply the diameter by the constant pi to calculate the circle circumference. For example, the circle diameter is 12.3 inches. Then the circumference is 38.6417 inches.
- 4). Consider the conversion of the circle circumference in another linear unit if necessary. For example, if it is calculate in inches multiply it by 2.54 to convert it to centimeters. But if it is expressed in centimeters multiply by 0.3937 to compute it in inches.
In our example, the circumference of 38.6417 inches will be converted to 38.6417 x 2.54 = 98.1499 cm.
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