How do you read a p i tape measure

Question

it is a tape ruler for pipe

Answer 1

Wrap it around the pipe. Align the zero with the next wrap of tape, and read the dimension nearest the zero. They are the same as inches or mm, but are 3.14x further apart. The pi tape actually measures the circumference, but is calibrated to give the equivalent diameter, i.e the diameter of the round pipe with the same circumference.