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How to Calculate the Diameter of a Tube

A tube represents any object of the cylindrical shape. The tube's cross-section is a circle. Tubes such as pipes are commonly used in building construction. You often may need to know a tube's diameter to make sure the tube fits in place. Calculate the diameter using the circumference of a tube or its radius.

Things You'll Need

Calculator
Measuring tape
Cleaning materials, if needed

Instructions

- 1
  Clean the tube, if it is needed, and make sure there is nothing on it or around it that would affect the measurement of its circumference, which is the distance around the outside of the tube.
- 2
  Measure the circumference of the tube with the measuring tape.
- 3
  Divide the circumference of the tube by the mathematical constant pi, which is 3.142 when rounded to three decimal places, to calculate the diameter. For example, if the circumference is 10.2 inches then the diameter is 10.2 / 3.142 = 3.246 inches.

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