Flange Dimensions Reference
Complete ASME B16.5 dimension tables for carbon flanges from 1/2" through 24", showing outer diameter, bore, bolt circle, number of bolts, bolt diameter, and face thickness across all pressure classes.
How to Use These Dimensions
ASME B16.5 is the standard specification for pipe flanges and flanged fittings in North America. These dimension tables apply to all flange types: blind, weld neck, slip-on, threaded, socket weld, and lap joint.
Select your nominal pipe size (NPS) and pressure class to find:
- OD - Outer diameter of flange
- Bore - Inside diameter (for weld neck, slip-on, threaded)
- BC - Bolt circle diameter (spacing between bolt holes)
- Bolts - Number of bolts in pattern
- BD - Bolt hole diameter
- Thickness - Face thickness (carbon flange height)
Dimension Tables by Size
1/2" Flanges
| Spec | OD | Bore | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|---|
| 150 PSI | 3.88" | 0.84" | 2.62" | 4 | 0.5" | 0.44" |
| 300 PSI | 4.25" | 0.84" | 3" | 4 | 0.5" | 0.56" |
| 600 PSI | 5" | 0.84" | 3.62" | 8 | 0.375" | 0.75" |
| 900 PSI | 5.5" | 0.84" | 4" | 8 | 0.375" | 0.88" |
| 1500 PSI | 6.5" | 0.84" | 4.75" | 8 | 0.375" | 1.12" |
| 2500 PSI | 8.5" | 0.84" | 6" | 8 | 0.5" | 1.62" |
3/4" Flanges
| Spec | OD | Bore | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|---|
| 150 PSI | 4.62" | 1.05" | 3.38" | 4 | 0.5" | 0.5" |
| 300 PSI | 5" | 1.05" | 3.75" | 4 | 0.5" | 0.62" |
| 600 PSI | 5.75" | 1.05" | 4.38" | 8 | 0.375" | 0.88" |
| 900 PSI | 6.38" | 1.05" | 4.75" | 8 | 0.375" | 1" |
| 1500 PSI | 7.62" | 1.05" | 5.5" | 8 | 0.375" | 1.25" |
| 2500 PSI | 9.62" | 1.05" | 6.75" | 8 | 0.5" | 1.88" |
1" Flanges
| Spec | OD | Bore | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|---|
| 150 PSI | 4.88" | 1.38" | 3.62" | 4 | 0.5" | 0.5" |
| 300 PSI | 5.5" | 1.38" | 4" | 4 | 0.5" | 0.69" |
| 600 PSI | 6.38" | 1.38" | 4.62" | 8 | 0.375" | 0.94" |
| 900 PSI | 7" | 1.38" | 5" | 8 | 0.375" | 1.12" |
| 1500 PSI | 8.28" | 1.38" | 5.75" | 8 | 0.375" | 1.44" |
| 2500 PSI | 10.28" | 1.38" | 7" | 8 | 0.5" | 2" |
1.5" Flanges
| Spec | OD | Bore | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|---|
| 150 PSI | 5.5" | 2.07" | 4.25" | 4 | 0.625" | 0.56" |
| 300 PSI | 6.12" | 2.07" | 4.75" | 4 | 0.625" | 0.75" |
| 600 PSI | 7.25" | 2.07" | 5.5" | 8 | 0.5" | 1" |
| 900 PSI | 8" | 2.07" | 6" | 8 | 0.5" | 1.19" |
| 1500 PSI | 9.5" | 2.07" | 6.75" | 8 | 0.5" | 1.56" |
| 2500 PSI | 11.5" | 2.07" | 8" | 8 | 0.625" | 2.19" |
2" Flanges
| Spec | OD | Bore | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|---|
| 150 PSI | 6" | 2.38" | 4.75" | 4 | 0.625" | 0.62" |
| 300 PSI | 6.75" | 2.38" | 5.25" | 8 | 0.5" | 0.81" |
| 600 PSI | 8" | 2.38" | 6" | 8 | 0.5" | 1.06" |
| 900 PSI | 8.75" | 2.38" | 6.62" | 8 | 0.5" | 1.31" |
| 1500 PSI | 10.28" | 2.38" | 7.5" | 12 | 0.375" | 1.69" |
| 2500 PSI | 12.28" | 2.38" | 8.75" | 12 | 0.5" | 2.31" |
2.5" Flanges
| Spec | OD | Bore | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|---|
| 150 PSI | 7" | 2.88" | 5.5" | 4 | 0.75" | 0.69" |
| 300 PSI | 7.75" | 2.88" | 6" | 8 | 0.5" | 0.88" |
| 600 PSI | 9" | 2.88" | 6.75" | 8 | 0.625" | 1.12" |
| 900 PSI | 10" | 2.88" | 7.5" | 8 | 0.625" | 1.44" |
| 1500 PSI | 11.5" | 2.88" | 8.5" | 12 | 0.5" | 1.81" |
| 2500 PSI | 14" | 2.88" | 10" | 12 | 0.625" | 2.56" |
3" Flanges
| Spec | OD | Bore | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|---|
| 150 PSI | 7.5" | 3.39" | 6" | 4 | 0.75" | 0.75" |
| 300 PSI | 8.25" | 3.39" | 6.62" | 8 | 0.625" | 0.94" |
| 600 PSI | 9.75" | 3.39" | 7.5" | 8 | 0.625" | 1.19" |
| 900 PSI | 10.75" | 3.39" | 8.25" | 8 | 0.625" | 1.56" |
| 1500 PSI | 12.5" | 3.39" | 9.25" | 12 | 0.5" | 1.94" |
| 2500 PSI | 15" | 3.39" | 10.75" | 12 | 0.75" | 2.69" |
4" Flanges
| Spec | OD | Bore | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|---|
| 150 PSI | 8.5" | 4.31" | 6.75" | 8 | 0.625" | 0.81" |
| 300 PSI | 9.5" | 4.31" | 7.5" | 8 | 0.625" | 1" |
| 600 PSI | 11" | 4.31" | 8.5" | 8 | 0.75" | 1.31" |
| 900 PSI | 12" | 4.31" | 9.25" | 12 | 0.625" | 1.69" |
| 1500 PSI | 14" | 4.31" | 10.5" | 12 | 0.625" | 2.06" |
| 2500 PSI | 16.5" | 4.31" | 12" | 12 | 0.75" | 2.81" |
6" Flanges
| Spec | OD | Bore | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|---|
| 150 PSI | 10.75" | 6.31" | 8.5" | 8 | 0.75" | 0.94" |
| 300 PSI | 11.75" | 6.31" | 9.5" | 8 | 0.75" | 1.12" |
| 600 PSI | 13.5" | 6.31" | 10.75" | 12 | 0.625" | 1.44" |
| 900 PSI | 14.75" | 6.31" | 11.75" | 12 | 0.625" | 1.81" |
| 1500 PSI | 16.5" | 6.31" | 13" | 12 | 0.75" | 2.19" |
| 2500 PSI | 19" | 6.31" | 15" | 16 | 0.75" | 3.06" |
8" Flanges
| Spec | OD | Bore | BC | Bolts | BD | Thickness |
|---|---|---|---|---|---|---|
| 150 PSI | 12.75" | 8.36" | 10.62" | 8 | 0.875" | 1.06" |
| 300 PSI | 14" | 8.36" | 11.75" | 8 | 0.875" | 1.31" |
| 600 PSI | 16" | 8.36" | 13.5" | 12 | 0.75" | 1.62" |
| 900 PSI | 17.5" | 8.36" | 14.75" | 12 | 0.75" | 2.06" |
| 1500 PSI | 19.75" | 8.36" | 16.5" | 16 | 0.625" | 2.44" |
| 2500 PSI | 23" | 8.36" | 19" | 16 | 0.875" | 3.38" |
Important Notes
Flanges & Fittings Specific
Blind flange thickness values shown are minimum face thickness to ASME B16.5 standards. Blind flanges are solid discs with bolt holes only; they have no bore. The "Bore" column shows the mounting bore for weld neck, slip-on, and threaded variants.
Pressure Classes
Pressure class determines the maximum allowable working pressure (MAWP) at rated temperature. Class 150 is standard industrial. Classes 300, 600, 900, 1500, 2500 are available for higher pressure applications. Always consult pressure-temperature ratings for your material grade.
Tolerances
ASME B16.5 specifies manufacturing tolerances on all dimensions. Bolt hole spacing (BC) typically has ±1/16" tolerance. Face thickness varies by pressure class. Request certified dimension reports for critical applications.
Surface Finish
Mating surfaces (faces) typically have 125 µin Ra finish per ASME B16.5. Stainless flanges may require higher polish. Food-grade applications require electropolish to 32 µin or better. Specify finish requirements when ordering.
Custom Dimensions
Non-standard bore diameters, overbore, custom bolt patterns, and special facings available via CNC machining. Contact us with your specific requirements for custom dimension drawings.
Need Certified Dimension Sheets?
For critical applications, we provide third-party certified dimension reports with actual as-manufactured measurements. Request custom dimension documentation for your specification.
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