NOMINAL NPT PIPE SIZE to NOMINAL METRIC SIZE CONVERSION CHART
NOMINAL PIPE SIZE (INCHES/U.S.)	NOMINAL PIPE SIZE (METRIC)
1/8"	6 mm
3/16"	7 mm
1/4"	8 mm
3/8"	10 mm
1/2"	15 mm
5/8"	18 mm
3/4"	20 mm
1"	25 mm
1-1/4"	32 mm
1-1/2"	40 mm
2"	50 mm
2-1/2"	65 mm
3"	80 mm
3-1/2"	90 mm
4"	100 mm
4-1/2"	115 mm
5"	125 mm
6"	150 mm