Connexion BSP / NPT and Common Thread Sizes Guide
 
Parallel Internal and External threads are Fastening Threads and require the use of a gasket or cone seal.

 

Tapered threads are Joining Threads and create a pressure tight seal when used with jointing compound or PTFE tape.
 
Pipe Thread Acronyms
NPT
American Standard Pipe Taper Thread (National Pipe Thread)
FPT
American Standard female Pipe Taper Thread
NPSC
American Standard Straight Coupling Pipe Thread
BSP
British Standard Pipe (can mean either BSPP or BSPT)
BSPP
British Standard Pipe Parallel
BSPT
British Standard Pipe Taper
GHT
Garden Hose Thread
G Thread
British Gas – Parallel (same as BSPP)
R Thread
British Tapered (same as BSPT)
 

 NPT – National Pipe Thread (US Standard)

Nominal Pipe Size
(Inches)
Thread per Inch
(TPI)
Outside Diameter (Inches)
Outside Diameter (mm)
1/8”
27
0.405
10.3
¼”
18
0.540
13.7
3/8
18
0.675
17.15
1/2
14
0.84
17.9
3/4
14
1.05
26.67
1
11.5
1.315
33.40
11/4
11.5
1.660
42.16
11/2
11.5
1.90
48.26
2
11.5
2.375
60.33
21/2
8
2.875
73.03

 

 BSP – British Straight and Tapered

Nominal Pipe Size
(Inches)
Thread per Inch
(TPI)
Outside Diameter (Inches)
Outside Diameter (mm)
1/8”
28
0.402
10.21
¼”
19
0.531
13.49
3/8
19
0.677
17.2
1/2
14
0.839
21.31
3/4
14
1.059
26.90
1
11
1.327
33.71
11/4
11
1.669
42.39
11/2
11
1.902
48.31
2
11
2.374
60.30
21/2
11
2.996
76.10

Straight Pipes Standards

NPSC - American Standard Straight Pipe Threads in Pipe Couplings Couplings
Applicable Standards
  • ANSI B1.20.1 PIPE THREADS, GENERAL PURPOSE (INCH)
  • FED-STD-H28/7 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 7 PIPE THREADS - GENERAL PURPOSE
NPSF - Dryseal American Standard Fuel Internal Straight Pipe Threads
Applicable Standards
  • SAE J476 DRYSEAL PIPE THREADS
  • ANSI B1.20.3 DRYSEAL PIPE THREADS (INCH)
  • FED-STD-H28/8 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 8 DRYSEAL PIPE THREADS
NPSI - Dryseal American Intermediate Internal Straight Pipe Threads
Applicable Standards
  • SAE J476 DRYSEAL PIPE THREADS
  • ANSI B1.20.3 DRYSEAL PIPE THREADS (INCH)
  • FED-STD-H28/8 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 8 DRYSEAL PIPE THREADS
NPSM - American Standard Straight Pipe Threads for Free-Fitting Mechanical Joints for Fixtures (these threads fit freely over NPTF threads. They are used in swivel nuts of 07 adapters)
Applicable Standards
  • ANSI B1.20.1 PIPE THREADS, GENERAL PURPOSE (INCH)
  • FED-STD-H28/7 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 7 PIPE THREADS - GENERAL PURPOSE

Taper Pipe Standards

ANPT - Aeronautical National Taper Pipe Threads
Applicable Standards
  • MIL-P-7105 PIPE THREADS, TAPER, AERONAUTICAL NATIONAL FORM, SYMBOL ANPT, GENERAL REQUIREMENTS
NPT - American Standard Taper Pipe Threads for General Use
Applicable Standards
  • ANSI B1.20.1 PIPE THREADS, GENERAL PURPOSE (INCH)
  • FED-STD-H28/7 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 7 PIPE THREADS - GENERAL PURPOSE
NPTF - Dryseal American Standard Taper Pipe Threads
Applicable Standards
  • SAE J476 DRYSEAL PIPE THREADS
  • ANSI B1.20.3 DRYSEAL PIPE THREADS (INCH)
  • FED-STD-H28/8 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 8 DRYSEAL PIPE THREADS

PTF - SAE Short - Dryseal SAE Short Taper Pipe Threads

PTF - SAE Short is mainly used in low pressure pneumatic and fuel applications.
Applicable Standards
  • ANSI B1.20.3 DRYSEAL PIPE THREADS (INCH)

PTF SPL Short & SPL Extra Short - Dryseal Special Short Taper Pipe Threads

Are used in some pneumatic components where shortened thread depth is required because of size limitations.

Applicable Standards
ANSI B1.20.3 DRYSEAL PIPE THREADS (INCH)

AWWA - American Water Works Association

  •  ANSI/AWWA C800-05 UNDERGROUND SERVICE LINE VALVES AND FITTINGS

Unified Thread Standards

UN - Unified Constant Pitch Threads (standard series: 4, 6, 8, 12, 16, 20, 28, 32)

Applicable Standards
ASME B1.1 UNIFIED INCH SCREW THREADS (UN & UNR THREAD FORM)

  • FED-STD-H28/2 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 2 UNIFIED INCH SCREW THREADS-UN AND UNR THREAD FORMS

UNC - Unified Coarse Threads

Applicable Standards
ASME B1.1 UNIFIED INCH SCREW THREADS (UN & UNR THREAD FORM)
  • FED-STD-H28/2 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 2 UNIFIED INCH SCREW THREADS-UN AND UNR THREAD FORMS
UNEF - Unifed Extra Fine Threads
Applicable Standards
  • ASME B1.1 UNIFIED INCH SCREW THREADS (UN & UNR THREAD FORM)
  • FED-STD-H28/2 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 2 UNIFIED INCH SCREW THREADS-UN AND UNR THREAD FORMS
UNF - Unified Fine Threads
Applicable Standards
  • ASME B1.1 UNIFIED INCH SCREW THREADS (UN & UNR THREAD FORM)
  • FED-STD-H28/2 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 2 UNIFIED INCH SCREW THREADS-UN AND UNR THREAD FORMS
UNS - Unified Special Pitch Threads
Applicable Standards
  • ASME B1.1 UNIFIED INCH SCREW THREADS (UN & UNR THREAD FORM)
  • SCREW-THREAD STANDARDS FOR FEDERAL SERVICES-SEC. 3
UNJ - Unified Controlled Root Radius Threads
Applicable Standards
  • ANSI B1.15 UNIFIED INCH SCREW THREADS (UNJ THREAD FORM)
  • FED-STD-H28/4 SCREW-THREAD STANDARDS FOR FEDERAL SERVICES SECTION 4 CONTROLLED RADIUS ROOT SCREW THREADS, UNJ SYMBOL

Metric Thread Standards

M - Metric Screw Threads M profile
Applicable Standards
  • ISO 261 ISO GENERAL PURPOSE METRIC SCREW THREADS - GENERAL PLAN
  • ASME B1.13M METRIC SCREW THREADS: M PROFILE
  • FED-STD-H28/21 METRIC SCREW-THREADS

M Keg Metric Taper Threads

Mainly used in Germany.
Applicable Standards
  • DIN 158-1 METRIC EXTERNAL TAPER SCREW THREADS AND MATING INTERNAL PARALLEL SCREW THREADS - PART 1. NOMINAL SIZES, LIMIT DEVIATIONS, LIMITS OF SIZE AND VERIFICATION
  • DIN 158-2 METRIC EXTERNAL TAPER SCREW THREAD AND MATING INTERNAL PARALLEL SCREW THREADS - PART 2. GAUGING SYSTEM, USE OF GAUGES, CALCULATION OF GAUGE DIMENSIONS AND GENERAL FEATURES

BSi - British Standards

R (BSPT) - British Standard Taper Pipe Threads, External
Applicable Standards
  • BS 21 PIPE THREADS FOR TUBES AND FITTINGS WHERE PRESSURE-TIGHT JOINTS ARE MADE ON THE THREADS (METRIC DIMENSIONS)
  • ISO 7/1 PIPE THREADS: DESIGNATION, DIMENSIONS/TOLERANCES
Rc (BSPT) - British Standard Taper Pipe Threads, Internal
Applicable Standards
  • BS 21 PIPE THREADS FOR TUBES AND FITTINGS WHERE PRESSURE-TIGHT JOINTS ARE MADE ON THE THREADS (METRIC DIMENSIONS)
  • ISO 7/1 PIPE THREADS: DESIGNATION, DIMENSIONS/TOLERANCES
Rp or G (BSPP) - British Standard Pipe (Parallel) Threads
Applicable Standards
  • BS 2779 PIPE THREADS FOR TUBES & FITTINGS WHERE PRESSURE-TIGHT JOINTS ARE NOT MADE ON THE THREADS (METRIC DIMENSIONS)
  • ISO 228/1 PIPE THREADS PT 1: DESIGNATION, DIMENSIONS, TOLERANCE

Japanese Standards

PF - JIS Parallel Pipe Threads

PF threads are functionally interchangeable with BSPP. This is an old designations replaced with G.
Applicable Standards
  • JIS B 202 PARALLEL PIPE THREADS
  • ISO 228/1 PIPE THREADS PT 1: DESIGNATION, DIMENSIONS, TOLERANCE

PT - JIS Taper Pipe Threads

PT threads are functionally interchangeable with BSPT threads. This is an old designations replaced with and R and Rc.
Applicable Standards
  • JIS B 0203 TAPER PIPE THREADS
  • ISO 7/1 PIPE THREADS: DESIGNATION, DIMENSIONS/TOLERANCES
PS - JIS Parallel Internal Pipe Threads (to mate with PT threads)
Applicable Standards
  • JIS B 0203 TAPER PIPE THREADS
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