NPT Pipe Thread Sizing Chart
NPT pipe thread measurements can get confusing, here's a handy chart to help you fit all your parts together seamlessly.

OD Actual
(inches)
Pipe Thread
Size
Threads
per Inch
5/16 1/16 27
32/79 1/ 8 27
27/50 1/ 4 18
27/40 3/ 8 18
21/25 1/ 2 14
1 1/20 3/ 4 14
1 23/73 1 11-1/2
1 33/50 1-1/4 11-1/2
1 9/10 1-1/2 11-1/2
2 3/ 8 2 11-1/2
2 7/ 8 2-1/2 8
3 1/ 2 3 8
4 3-1/2 8
4 1/ 2 4 8
5 49/87 5 8
6 5/ 8 6 8
8 5/ 8 8 8
10 3/ 4 10 8
12 3/ 4 12 8