4" NPT Thread Specs
Standard: ASME B1.20.1 (NPT)
Technical parameters and design data for the 4" NPT pipe thread.
Established under standard ASME B1.20.1, this thread uses a pitch of 0.125 inches and has 8 threads per inch.
Often used in fluid, hydraulic, or pneumatic systems, NPT/BSP threads require suitable thread sealants to assure leak-tight performance.
Dimensional Specifications
Size Designation
4" NPT
Nominal Diameter
4.5 in(114.3 mm)
Major Diameter
4.9313 in(125.26 mm)
TPI (Threads per Inch)
8
Pitch
0.125 in
Pitch Diameter
4.8501 in(123.19 mm)
Minor Diameter
4.796 in(121.82 mm)
Tap Drill size
4-1/4 in
Quick Unit Converter
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Frequently Asked Questions
What is the tap drill size for 4" NPT pipe thread?
The recommended tap drill size for a 4" NPT pipe thread is 4-1/4 inches.
What is the major diameter of a 4" NPT pipe thread?
For a standard 4" NPT pipe thread, the major diameter at the pipe reference plane is 4.9313 inches (approx. 125.26 mm).