National Pipe Size/DN Conversion Chart

NPS DN
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