Basic NPT Pipe Thread Information

Engagement length when tight

(see below)

  • Most ordering mistakes are caused by measuring the pipe size of the fitting or component incorrectly.
  • The nominal size of any pipe does not in fact refer to either the outside diameter (O.D.) or the inside diameter (I.D.) of the pipe.
  • The table lists standard pipe sizes along with the actual O.D. and I.D. for each size.
  • Keep in mind that manufacturers may slightly modify these dimensions to strengthen or enhance the performance of a product.
Pipe
Size
(NPT)
Threads
Per Inch
Outside Dia.
of Pipe
Inside Dia.
of Pipe

Without Ream

With Ream

E
1/16 27 .312 .209 1/4 15/64 .250
1/8 .405 .269 11/32 21/64 .250
1/4 18 .540 .364 7/16 27/64 .300
3/8 .675 .493 9/16 9/16 .300
1/2 14 .840 .622 45/64 11/16 .420
3/4 1.050 .824 29/32 57/64 .545
1 11 1/2 1.315 1.049 1 9/64 1 1/8 .661
1 1/4 1.660 1.380 1 31/64 1 15/32 .681
1 1/2 1.900 1.610 1 23/32 1 45/64 .681
2 2.375 2.067 2 3/16 2 11/64 .697

Tap Drill Sizes

Once the correct pipe size has been determined,  the engagement dimension "E" may be used to determine the overall length of the component required to assemble properly when fully  tightened.

Pipe Check

PC-100 simply determines the size of pipes from 1/16" to 1/2" NPT.

 

Made entirely of heavy gauge aluminum, this model is perfect for the office, warehouse, or factory floor.

 

Just turn the thread into the hole that fits to determine pipe size.

  • Finest quality - MADE IN USA
  • Anodized aluminum construction
  • Each pipe size is clearly marked

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