Fire Hose Thread Adapter ID Reference
Commonly Used U.S. Fire Hose Adapter Threads
| Size (inch) | NST/NH Outside Diameter Male (in) | NST/NH Outside Diameter Male (Decimals) | TPI | NPSH Outside Diameter Male (in) | NPSH Outside Diameter Male (Decimals) | NPT Outside Diameter Male (in) | NPT Outside Diameter Male (Decimals) | TPI |
| 3/4 | – | – | – | 1 | 1.03 | 1 | .98 | 14 |
| 1 | 1 3/8 | 1.37 | 8 | 1 184 | 1.29 | 1 1/4 | 1.23 | 11 1/2 |
| 1 1/2 | 2 | 1.99 | 9 | 1 7/8 | 1.87 | 1 7/8 | 1.87 | 11 1/2 |
| 2 | 2 1/2 | 2.51 | 8 | 2 23/8 | 2.35 | 2 5/16 | 2.29 | 11 1/2 |
| 2 1/2 | 3 1/16 | 3.06 | 7 1/2 | 2 13/16 | 2.84 | 2 3/4 | 2.76 | 8 |
| 3 | 3 5/8 | 3.62 | 6 | 3 14/2 | 3.47 | 3 3/8 | 3.38 | 8 |
| 3 1/2 | 4 1/2 | 4.24 | 6 | 4 | 3.97 | 3 7/8 | 3.88 | 8 |
| 4 | 5 | 5.01 | 4 | 4 1/2 | 4.47 | 4 3/8 | 4.38 | 8 |
| 4 1/2 | 5 3/4 | 5.76 | 4 | 5 | 4.97 | – | – | 8 |
| 5 | 6 1/4 | 6.26 | 4 | 5 9/16 | 5.56 | 5 7/16 | 5.44 | 8 |
| 6 | 7 | 7.02 | 4 | 6 5/8 | 6.62 | 6 1/2 | 6.50 | 8 |
Commonly Used U.S. Fire Adapter Circumference
| Size (inch) | NST/NH Circumference (in) | NPSH Circumference (in) | NPT Circumference (in) |
| 3/4 | – | 3 1/4 | 3 1/8 |
| 1 | 4 5/16 | 4 1/16 | 3 7/8 |
| 1 1/2 | 6 1/4 | 5 7/8 | 5 3/4 |
| 2 | 7 7/8 | 7 3/8 | 7 1/4 |
| 2 1/2 | 9 5/8 | 8 15/16 | 8 11/16 |
| 3 | 11 3/8 | 10 7/8 | 10 5/8 |
| 3 1/2 | 13 5/16 | 12 1/2 | 12 1/4 |
| 4 | 15 3/4 | 14 1/32 | 13 3/4 |
| 4 1/2 | 18 1/8 | 15 19/32 | – |
| 5 | 19 21/32 | 17 21/32 | 17 1/8 |
| 6 | 22 1/16 | 20 13/16 | 20 1/2 |
Other U.S. Standard 2 1/2″ Adapter Threads
| City | Outside Diameter Male (in) | Outside Diameter (decimals) | TPI |
| British Pipe BSP | 2 31/32 | 2.96 | 11 |
| New York Corp NYC | 3 | 3.00 | 8 |
| New York City FD FDNY | 3 1/32 | 3.03 | 8 |
| Pacific Coast PCT | 3 1/32 | 3.03 | 7 1/2 |
| Chicago Hose | 3 3/64 | 3.04 | 7 |
| Chicago Fire Dept CFD | 3 | 3.00 | 7 1/2 |
| Buffalo, NY | 3 1/16 | 3.06 | 8 |
| Cincinnati, OH (new) | 3 1/16 | 3.06 | 6 |
| Cleveland, OH | 3 5/64 | 3.07 | 8 |
| Denver, CO | 3 3/32 | 3.09 | 8 |
| Detroit, MI | 3 1/8 | 3.12 | 7 1/2 |
| Omaha, NE | 3 5/64 | 3.07 | 8 |
| Phoenix, AZ (old) | 3 1/16 | 3.06 | 6 |
| Pittsburg, PA | 3 1/16 | 3.06 | 6 |
| Salt Lake City, UT | 3 1/4 | 3.25 | 6 |
| Toledo, OH | 3 | 3.00 | 8 |
Canadian Standard 2 1/2″ Adapter Threads
| Outside Diameter Male (in) | Outside Diameter (decimals) | TPI | ||
| AMA | Alberta Mutual Aid | 3 | 2.99 | 8 |
| BCT | British Columbia | 3 | 3.00 | 8 |
| CSA | Canadian Standards Assoc. | 3 1/8 | 3.12 | 5 |
| QST | Province of Quebec Std. | 3 1/32 | 3.03 | 7 |
| WCT | Western Canada Fire Under | 3 1/4 | 3.25 | 6 |
| NOVA | Nova Scotia -Zone 1 | 3 15/64 | 3.23 | 5 |
| QMT | Quebec/Montreal Combination | 3 1/32 | 3.03 | 7 |
Garden Hose Adapter Connection
| Size (in) | Outside Diameter (in) | Outside Diameter (decimals) | TPI | Circumference in Inches |
| 3/4 | 1 1/16 | 1.06 | 11 1/2 | 3 11/16 |
