Pipe size is the accepted industry designation, not the actual measured size. To determine pipe size, first use a ruler to measure the outside diameter (OD) for male ends or inside diameter (ID) for female ends. Then, round up the measurement to the closest OD or ID listed in the chart and select the corresponding pipe size. For example, if the OD or ID measures 1 3/16", the next highest OD or ID in the chart is 1 3/8", and the corresponding pipe size is 1".
Use OD for a male threaded end.
Use ID for a female threaded end.
Code:
Threaded OD or ID 3/8" 1/2" 5/8" 3/4" 1" 1 3/8" 1 5/8" 1 7/8" 2 3/8" 2 7/8" 3 1/2" 4 1/2"
Pipe Size 1/8" 1/4" 3/8" 1/2" 3/4" 1" 1 1/4" 1 1/2" 2" 2 1/2" 3" 4"