ANSI B1.20.1 - NPT - American National Standard Taper Pipe Threads

• NPT - National Pipe Thread Tapered - is a U.S. standard for tapered threads used to join pipes and fittings is defined by ANSI B1.20.1 Pipe Threads, General Purpose, Inch
• NPTF - National Pipe Thread Tapered Fine - also called Dryseal American National Standard Taper Pipe Thread -is a U.S. standard for tapered threads used to join pipes and fittings is defined by ANSI B1.20.3

For NPT threads a sealant compound or Polytetrafluoroethylene (PTFE) tape must be used for a leak-free seal. For NPTF no sealant is needed for a leak tight connection. NPTF threads are the same basic shape but with crest and root heights adjusted for an interference fit, eliminating the spiral leakage path.

NPT threads may be referred to as MPT ('Male Pipe Thread'), MNPT, or NPT(M) for male (external) threads, and FPT ('Female Pipe Thread'), FNPT, or NPT(F) for female (internal) threads. Note that FPT and MPT are not authorized designations per the ANSI standard.

Characteristics of NPT (also known as ANSI/ASME B1.20.1 Pipe Threads, General Purpose):

• the angle between the taper and the center axis of the pipe is  1^o 47' 24'' (1.7899^o)
  
• truncation of roots and crests are flat
• 60^o thread angle
• pitch is measured in threads per inch - TPI

Note! Pipe sizes do not refer to any physical dimensions. The outside diameter of a pipe or fitting must be measured and compared to a table for size identification. A 3/4" NPT pipe thread has an outside diameter - OD - of 1.050 inches. Each thread size has a defined number of threads per inch - TPI, or pitch. The 3/4" NPT pipe thread has 14 threads per inch. Both the TPI and OD of the thread are required for positive identification of thread size because more than one size have the same TPI.

For full table with Tap Drill Sizes - rotate the screen!

¹⁾ The taper rate is 1 in 16 inch (3/4 inch in a foot or 62.5 mm in a meter)

• TPI = threads per inch
• 1 inch = 25.4 mm

NPT threads are not interchangeable with NPS - National Pipe Straight - threads.

Example - Typical Designation of NPT thread:

• 1⁄8–27 NPT

NPT threads may look similar to ISO 7-1 threads. However, ISO and NPT threads should not be mixed. ISO threads have 55^o taper angle versus 60^o for NPT. The NPT root and crest configurations are also different from ISO. For ISO threads pitch is usually measured in millimeters (may be expressed in Inch). The pitch is different.

• NPS - American National Standard Straight Pipe Thread

Note that both NPT and NPS have the same thread angle, shape, and pitch (threads per inch). However, NPT threads are tapered and NPS threads are straight (parallel). Both threads have a 60° included angle and flat peaks and valleys.

Temperature ^oC
K
^oF

Length m
km
in
ft
yards
miles
naut miles

Area m²
km²
in²
ft²
miles²
acres

Volume m³
liters
in³
ft³
us gal

Weight kg_f
N
lbf

Velocity m/s
km/h
ft/min
ft/s
mph
knots

Pressure Pa
bar
mm H₂O
kg/cm²
psi
inches H₂O

Flow m³/s
m³/h
US gpm
cfm