FittingKey

Charts

Identification sheet

Pipe threads: NPT, BSPP and BSPT

The three pipe-thread families, by trade size. The trade size is neither the thread diameter nor the bore, which is why a 1/4 in pipe thread measures about 13 mm across the threads.

32 rows3 sectionsLandscape

Pipe threads: NPT, BSPP and BSPT

32 rows. Print landscape.

Pipe threads: NPT, BSPP and BSPT. The three pipe-thread families, by trade size. The trade size is neither the thread diameter nor the bore, which is why a 1/4 in pipe thread measures about 13 mm across the threads.
SizeThreadTPI / pitchBasic major ØMeasured across crestsTube ODWorking pressure
American National Pipe Taper, NPT (ASME B1.20.1) and NPTF dryseal (ASME B1.20.3)
1/16 NPT1/16-27 NPT27 TPI (0.941 mm pitch)7.94 mm / 0.313 inNot publishedNot publishedNot published
1/8 NPT1/8-27 NPT27 TPI (0.941 mm pitch)10.29 mm / 0.405 in9.9 mm to 10.41 mmNot published5,000 psi (345 bar)
1/4 NPT1/4-18 NPT18 TPI (1.411 mm pitch)13.72 mm / 0.54 in13.2 mm to 13.9 mmNot publishedNot published
3/8 NPT3/8-18 NPT18 TPI (1.411 mm pitch)17.15 mm / 0.675 in16.6 mm to 17.3 mmNot publishedNot published
1/2 NPT1/2-14 NPT14 TPI (1.814 mm pitch)21.34 mm / 0.84 in20.6 mm to 21.6 mmNot published3,000 psi (207 bar)
3/4 NPT3/4-14 NPT14 TPI (1.814 mm pitch)26.67 mm / 1.05 in26 mm to 27 mmNot published2,500 psi (172 bar)
1 NPT1-11 1/2 NPT11.5 TPI (2.209 mm pitch)33.4 mm / 1.315 in32.5 mm to 33.7 mmNot published2,000 psi (138 bar)
1 1/4 NPT1 1/4-11 1/2 NPT11.5 TPI (2.209 mm pitch)42.16 mm / 1.66 in41.2 mm to 42.5 mmNot published1,150 psi (79 bar)
1 1/2 NPT1 1/2-11 1/2 NPT11.5 TPI (2.209 mm pitch)48.26 mm / 1.9 in47.3 mm to 48.6 mmNot published1,000 psi (69 bar)
2 NPT2-11 1/2 NPT11.5 TPI (2.209 mm pitch)60.33 mm / 2.375 in59.3 mm to 60.7 mmNot published1,000 psi (69 bar)
British Standard Pipe Parallel, BSPP or G (ISO 228-1)
G 1/16G 1/16 (28 TPI, 55 degree)28 TPI (0.907 mm pitch)7.72 mm / 0.304 inNot publishedNot publishedNot published
G 1/8G 1/8 (28 TPI, 55 degree)28 TPI (0.907 mm pitch)9.73 mm / 0.383 in9.6 mm to 9.7 mmNot publishedNot published
G 1/4G 1/4 (19 TPI, 55 degree)19 TPI (1.337 mm pitch)13.16 mm / 0.518 in13 mm to 13.2 mmNot publishedNot published
G 3/8G 3/8 (19 TPI, 55 degree)19 TPI (1.337 mm pitch)16.66 mm / 0.656 in16.5 mm to 16.7 mmNot publishedNot published
G 1/2G 1/2 (14 TPI, 55 degree)14 TPI (1.814 mm pitch)20.95 mm / 0.825 in20.8 mm to 20.9 mmNot publishedNot published
G 5/8G 5/8 (14 TPI, 55 degree)14 TPI (1.814 mm pitch)22.91 mm / 0.902 in22.8 mm to 22.9 mmNot publishedNot published
G 3/4G 3/4 (14 TPI, 55 degree)14 TPI (1.814 mm pitch)26.44 mm / 1.041 in26.3 mm to 26.4 mmNot publishedNot published
G 7/8G 7/8 (14 TPI, 55 degree)14 TPI (1.814 mm pitch)30.2 mm / 1.189 inNot publishedNot publishedNot published
G 1G 1 (11 TPI, 55 degree)11 TPI (2.309 mm pitch)33.25 mm / 1.309 in33.1 mm to 33.2 mmNot publishedNot published
G 1 1/4G 1 1/4 (11 TPI, 55 degree)11 TPI (2.309 mm pitch)41.91 mm / 1.65 in41.8 mm to 41.9 mmNot publishedNot published
G 1 1/2G 1 1/2 (11 TPI, 55 degree)11 TPI (2.309 mm pitch)47.8 mm / 1.882 in47.7 mm to 47.8 mmNot publishedNot published
G 2G 2 (11 TPI, 55 degree)11 TPI (2.309 mm pitch)59.61 mm / 2.347 in59.5 mm to 59.6 mmNot publishedNot published
British Standard Pipe Taper, BSPT, R external and Rc internal (ISO 7-1)
R 1/16R 1/16 (28 TPI, 55 degree, taper 1:16)28 TPI (0.907 mm pitch)7.72 mm / 0.304 inNot publishedNot publishedNot published
R 1/8R 1/8 (28 TPI, 55 degree, taper 1:16)28 TPI (0.907 mm pitch)9.73 mm / 0.383 in9.5 mm to 10.1 mmNot publishedNot published
R 1/4R 1/4 (19 TPI, 55 degree, taper 1:16)19 TPI (1.337 mm pitch)13.16 mm / 0.518 in12.8 mm to 13.6 mmNot publishedNot published
R 3/8R 3/8 (19 TPI, 55 degree, taper 1:16)19 TPI (1.337 mm pitch)16.66 mm / 0.656 in16.3 mm to 17.1 mmNot publishedNot published
R 1/2R 1/2 (14 TPI, 55 degree, taper 1:16)14 TPI (1.814 mm pitch)20.95 mm / 0.825 in20.4 mm to 21.5 mmNot publishedNot published
R 3/4R 3/4 (14 TPI, 55 degree, taper 1:16)14 TPI (1.814 mm pitch)26.44 mm / 1.041 in25.9 mm to 27 mmNot publishedNot published
R 1R 1 (11 TPI, 55 degree, taper 1:16)11 TPI (2.309 mm pitch)33.25 mm / 1.309 in32.6 mm to 33.9 mmNot publishedNot published
R 1 1/4R 1 1/4 (11 TPI, 55 degree, taper 1:16)11 TPI (2.309 mm pitch)41.91 mm / 1.65 in41.1 mm to 42.6 mmNot publishedNot published
R 1 1/2R 1 1/2 (11 TPI, 55 degree, taper 1:16)11 TPI (2.309 mm pitch)47.8 mm / 1.882 in47 mm to 48.5 mmNot publishedNot published
R 2R 2 (11 TPI, 55 degree, taper 1:16)11 TPI (2.309 mm pitch)59.61 mm / 2.347 in58.6 mm to 60.5 mmNot publishedNot published

Sources: ANSI/ASME B1.20.1, Pipe Threads, General Purpose (Inch), Table 1 (ASME); ISO 228-1, Pipe threads where pressure-tight joints are not made on the threads, Table 1 (ISO); ISO 7-1, Pipe threads where pressure-tight joints are made on the threads, Table 1 (ISO); Hydraulic coupling identification chart E2/50101 (Gates); Fluid Ports and Connectors Identification Guide (McGill Hose & Coupling); Master catalogue: conformance, working pressure and torque tables (Tompkins Industries); Catalogue page 4: SAE J514 working pressure ratings, and SAE J1453 working, proof and minimum burst pressures for face seal fittings (Brennan Industries); Thread and connector identification guide (Gerrard Hydraulics (RYCO)); How to identify British threads and fittings (Adaptall); Thread identification: BSP, JIC, ORFS and metric tables (Apex Fluid Power); NPT thread chart (AmesWeb); BSPP thread chart and calculator (AmesWeb); NPT thread charts (Machining Doctor); BSP thread charts, BSPP and BSPT (Machining Doctor).

Reference aid for identification and ordering, not a substitute for the manufacturer specification. Pressure ratings apply only under the conditions printed beside them. Verify against the maker's catalogue before a system is charged.

Free to read

Every figure on this sheet, on its own page

Nothing on this sheet is behind the paywall as information. Each standard below has a free index carrying the same table, and each size has its own page with the measured span, the seat, what it mates with and the sources behind every figure.

NPT / NPTF10 sizes, freeASME B1.20.1, ASME B1.20.3BSPP (G)12 sizes, freeISO 228-1, BS 2779BSPT (R)10 sizes, freeISO 7-1, BS 21

More sheets

Other identification charts

SAE inch fittings: JIC 37, ORB, ORFS and SAE 4542 rowsMetric DIN 2353 / ISO 8434-1, light and heavy series20 rowsJapanese fittings: JIS 30 degree and Komatsu 30 degree16 rowsSeat and thread identification: all ten standards10 rowsPublished working pressures, with the conditions they apply under61 rows

Where these figures come from

Every value on this page was checked against 14 independent published sources: