EQU - National Pipe Thread Taper

Created by Kathleen Patrick, Modified on Wed, 11 Dec at 2:35 PM by Kathleen Patrick

American National Standard Pipe Thread standards, often called national pipe thread standards for short, are United States national technical standards for screw threads used on threaded pipes and pipe fittings. They include both tapered and straight thread series for various purposes, including rigidity, pressure-tight sealing, or both. The types are named with a full name and an abbreviation, such as NPT, NPS, NPTF, or NPSC.


NPT ‐ National Pipe Thread Taper ‐ ANSI B1.20.1
Pipe Size
Threads/InchApprox. Length
of Thread
Approx. Number
of Threads to be cut
Nominal Outside Pipe DiameterTap Drill
1/8"273/8"100.405" 
1/4"185/8"110.540"7/16"
3/8"185/8"110.675"37/64"
1/2"143/4"100.840"23/32"
3/4"143/4"101.050"59/64"
1"11‐1/27/8"101.315"1‐5/32"
1‐1/4"11‐1/21"111.660"1‐1/2"
1‐1/2"11‐1/21"111.900"1‐47/64"
2"11‐1/21"112.375"2‐7/32"
2‐1/2"81‐1/2"122.875"2‐5/8"

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