Nominal Pipe Size to Metric Conversion Chart

NPS (Inches)	DN (Millimeters)
1/8"	6
3/16"	7
1/4"	8
3/8"	10
1/2"	15
5/8"	18
3/4"	20
1"	25
1-1/4"	32
1-1/2"	40
2"	50
2-1/2"	65
3"	80
3-1/2"	90
4"	100
4-1/2"	115
5"	125
6"	150