The tables below list all the relevant size information for gaskets made to suit ANSI B16.5 flanges in the Ring Face (i.e. no bolt holes) style.
This covers ANSI 150, ANSI 300, ANSI 600, ANSI 900 and ANSI 1500 specifications.
In some cases (especially with smaller gaskets but not limited to these) a certain nominal bore gasket will fit both either ANTI 150 & 600 or ANSI 900 & 1500E flanges. When this occurs it is noted in the Matches Table column of the table(s).
What this means in practice is…
ANSI 150
Does not share it’s sizing with any other flange table at any nominal bore.
ANSI 300
Shares it’s sizing with ANSI 600 up to 80NB (3”). For pipes larger than this, individual gaskets are offered as the sizes differ.
ANSI 600
Shares it’s sizing with ANSI 300 up to 80NB (3”). For pipes larger than this, individual gaskets are offered as the sizes differ.
ANSI 900
Shares it’s sizing with ANSI 1500 up to 65NB (2.5”). For pipes larger than this, individual gaskets are offered as the sizes differ.
ANSI 1500
Shares it’s sizing with ANSI 900 up to 65NB (2.5”). For pipes larger than this, individual gaskets are offered as the sizes differ.
This style of gasket is designed to sit inside the bolts of the flanges and is known by quite a few names, including:
- RF Flange Gaskets.
- IBC Gaskets (Inner Bolt Circle).
- Raised Face Gaskets (as they are often used on raised face type flanges).
- Ring Face Gaskets.
Gasket Measurement Terms Used.
Gasket OD: Outside Diameter of the Gasket.
Gasket ID: Inside Diameter of the Gasket (Centre Hole). If there is no centre hole it is known as a "Blind Gasket". These are typically used at the end of pipelines and can be produced upon request.
ANSI Flange Dimensions Quick Links.
Click any of the buttons below to go directly to that flange table sizing information.
Class 150 Ring Face Flange Gasket Size Table.
All Dimensions below are given in millimeters (mm).
| Flange Nominal Bore |
Imperial Short-Hand |
Gasket ID | Gasket OD | Matches Table |
| 15NB | 1/2" | 21 | 48 | - |
| 20NB | 3/4" | 27 | 57 | - |
| 25NB | 1" | 33 | 67 | - |
| 32NB | 1 1/4" | 42 | 76 | - |
| 40NB | 1 1/2" | 48.4 | 86 | - |
| 50NB | 2" | 60.3 | 105 | - |
| 65NB | 2 1/2" | 73 | 124 | - |
| 80NB | 3" | 89 | 136.5 | - |
| 90NB | 3 1/2" | 102 | 162 | - |
| 100NB | 4" | 114.3 | 175 | - |
| 125NB | 5" | 141.3 | 197 | - |
| 150NB | 6" | 168 | 222 | - |
| 200NB | 8" | 219 | 279 | - |
| 250NB | 10" | 273 | 340 | - |
| 300NB | 12" | 324 | 410 | - |
| 350NB | 14" | 356 | 450 | - |
| 400NB | 16" | 406 | 515 | - |
| 450NB | 18" | 457 | 550 | - |
| 500NB | 20" | 508 | 605 | - |
| 600NB | 24" | 610 | 715 | - |
Class 300 Ring Face Flange Gasket Size Table.
All Dimensions below are given in millimeters (mm).
| Flange Nominal Bore |
Imperial Short-Hand |
Gasket ID | Gasket OD | Matches Table |
| 15NB | 1/2" | 21 | 54 | ANSI 600 |
| 20NB | 3/4" | 27 | 67 | ANSI 600 |
| 25NB | 1" | 33 | 73 | ANSI 600 |
| 32NB | 1 1/4" | 42 | 83 | ANSI 600 |
| 40NB | 1 1/2" | 48.4 | 95 | ANSI 600 |
| 50NB | 2" | 60.3 | 111 | ANSI 600 |
| 65NB | 2 1/2" | 73 | 130 | ANSI 600 |
| 80NB | 3" | 89 | 149 | ANSI 600 |
| 90NB | 3 1/2" | 102 | 165 | - |
| 100NB | 4" | 114.3 | 181 | - |
| 125NB | 5" | 141.3 | 216 | - |
| 150NB | 6" | 168 | 251 | - |
| 200NB | 8" | 219 | 308 | - |
| 250NB | 10" | 273 | 362 | - |
| 300NB | 12" | 324 | 422 | - |
| 350NB | 14" | 356 | 486 | - |
| 400NB | 16" | 406 | 540 | - |
| 450NB | 18" | 457 | 597 | - |
| 500NB | 20" | 508 | 654 | - |
| 600NB | 24" | 610 | 775 | - |
Class 600 Ring Face Flange Gasket Size Table.
All Dimensions below are given in millimeters (mm).
| Flange Nominal Bore |
Imperial Short-Hand |
Gasket ID | Gasket OD | Matches Table |
| 15NB | 1/2" | 21 | 54 | ANSI 300 |
| 20NB | 3/4" | 27 | 67 | ANSI 300 |
| 25NB | 1" | 33 | 73 | ANSI 300 |
| 32NB | 1 1/4" | 42 | 83 | ANSI 300 |
| 40NB | 1 1/2" | 48.4 | 95 | ANSI 300 |
| 50NB | 2" | 60.3 | 111 | ANSI 300 |
| 65NB | 2 1/2" | 73 | 130 | ANSI 300 |
| 80NB | 3" | 89 | 149 | ANSI 300 |
| 90NB | 3 1/2" | 102 | 162 | - |
| 100NB | 4" | 114.3 | 194 | - |
| 125NB | 5" | 141.3 | 241 | - |
| 150NB | 6" | 168 | 267 | - |
| 200NB | 8" | 219 | 320.7 | - |
| 250NB | 10" | 273 | 400 | - |
| 300NB | 12" | 324 | 457 | - |
| 350NB | 14" | 356 | 492 | - |
| 400NB | 16" | 406 | 565 | - |
| 450NB | 18" | 457 | 613 | - |
| 500NB | 20" | 508 | 683 | - |
| 600NB | 24" | 610 | 791 | - |
Class 900 Ring Face Flange Gasket Size Table.
All Dimensions below are given in millimeters (mm).
| Flange Nominal Bore |
Imperial Short-Hand |
Gasket ID | Gasket OD | Matches Table |
| 15NB | 1/2" | 21 | 64 | ANSI 1500 |
| 20NB | 3/4" | 27 | 70 | ANSI 1500 |
| 25NB | 1" | 33 | 79 | ANSI 1500 |
| 32NB | 1 1/4" | 42 | 89 | ANSI 1500 |
| 40NB | 1 1/2" | 48.4 | 98 | ANSI 1500 |
| 50NB | 2" | 60.3 | 143 | ANSI 1500 |
| 65NB | 2 1/2" | 73 | 165 | ANSI 1500 |
| 80NB | 3" | 89 | 168 | - |
| 90NB | 3 1/2" | N/A | N/A | - |
| 100NB | 4" | 114.3 | 206 | - |
| 125NB | 5" | 141.3 | 248 | - |
| 150NB | 6" | 168 | 289 | - |
| 200NB | 8" | 219 | 359 | - |
| 250NB | 10" | 273 | 435 | - |
| 300NB | 12" | 324 | 498 | - |
| 350NB | 14" | 356 | 520 | - |
| 400NB | 16" | 406 | 575 | - |
| 450NB | 18" | 457 | 638 | - |
| 500NB | 20" | 508 | 699 | - |
| 600NB | 24" | 610 | 840 | - |
Class 1500 Ring Face Flange Gasket Size Table.
All Dimensions below are given in millimeters (mm).
| Flange Nominal Bore |
Imperial Short-Hand |
Gasket ID | Gasket OD | Matches Table |
| 15NB | 1/2" | 21 | 64 | ANSI 900 |
| 20NB | 3/4" | 27 | 70 | ANSI 900 |
| 25NB | 1" | 33 | 79 | ANSI 900 |
| 32NB | 1 1/4" | 42 | 89 | ANSI 900 |
| 40NB | 1 1/2" | 48.4 | 98 | ANSI 900 |
| 50NB | 2" | 60.3 | 143 | ANSI 900 |
| 65NB | 2 1/2" | 73 | 165 | ANSI 900 |
| 80NB | 3" | 89 | 175 | - |
| 90NB | 3 1/2" | N/A | N/A | - |
| 100NB | 4" | 114.3 | 210 | - |
| 125NB | 5" | 141.3 | 254 | - |
| 150NB | 6" | 168 | 283 | - |
| 200NB | 8" | 219 | 352 | - |
| 250NB | 10" | 273 | 435 | - |
| 300NB | 12" | 324 | 520 | - |
| 350NB | 14" | 356 | 580 | - |
| 400NB | 16" | 406 | 641 | - |
| 450NB | 18" | 457 | 705 | - |
| 500NB | 20" | 508 | 755 | - |
| 600NB | 24" | 610 | 901 | - |
Other Flange Specification Sizing
If the gasket size you're looking for isn't listed on any of the above tables it may suit a different flange spec. We have sizing tables for many of the most common ones used in Australia. You can access our current list via our Flange Table Gasket Dimensions Menu Page.
For more information, help finding the correct sizing or to enquire about custom cut gaskets in all kinds of materials and sizes, please do contact us.