Determine whether you need the pipe’s outside diameter, inside diameter, or length
Use a tape measure or ruler for length
Measure the pipe’s outside diameter across the widest point
Measure the pipe’s inside diameter across the opening if accessible
Measure the circumference with a flexible tape if diameter is hard to access
Divide circumference by 3.1416 to get diameter
Check the pipe size marking if available
Use calipers for more precise diameter measurements
Measure from end to end for total pipe length
Measure the wall thickness if needed by comparing outside and inside diameters
Record measurements in the required unit
Verify the measurement at more than one point if the pipe is not perfectly round