Specifications of International Thread Standards

American Taper Pipe Thread, with sealant compound. National Pipe Taper (1:16)
The flank angle is 60°, the profile was originated by William Sellers.

Nominal DiameterMajor Diameter
mm
Tapping
Drill Size
mm
TPIPitch
mm
1/16" - 27 NPT7.8956.00270.941
1/8" - 27 NPT10.2428.25270.941
1/4" - 18 NPT13.61610.70181.411
3/8" - 18 NPT17.05514.10181.411
1/2" - 14 NPT21.22317.40141.814
3/4" - 14 NPT26.56822.60141.814
1" - 11 1/2 NPT33.22828.5011.52.209
1 1/4" - 11 1/2 NPT41.98537.0011.52.209
1 1/2" - 11 1/2 NPT48.05443.5011.52.209
2" - 11 1/2 NPT60.09255.0011.52.209
2 1/2" - 8 NPT72.69965.5083.175
3" - 8 NPT88.60881.5083.175
3 1/2" - 8 NPT101.31694.3083.175
4" - 8 NPT113.973107.0083.175
5" - 8 NPT141.300134.38483.175
6" - 8 NPT168.275161.19183.175
8" - 8 NPT219.075211.67383.175
10" - 8 NPT273.050265.31183.175
12" - 8 NPT323.850315.79383.175
NPT