Flange Dimensions
Chart
Flange dimensions, bolt circle and pressure class information per ASME B16.5 and EN 1092-1 standards.
Flange Dimension Lookup
Selected Size: NPS 2" (DN50) | Standard: ASME B16.5
| Pressure Class | OD mm | Thickness mm | PCD mm | Bolt Qty | Bolt Size |
|---|---|---|---|---|---|
| Class 150 | 152 | 19 | 120.7 | 4 | M16 |
| Class 300 | 165 | 22 | 127 | 8 | M16 |
| Class 600 | 165 | 26 | 127 | 8 | M16 |
| Class 900 | 216 | 35 | 165.1 | 8 | M22 |
| Class 1500 | 216 | 38 | 165.1 | 8 | M22 |
| Class 2500 | 235 | 51 | 177.8 | 8 | M26 |
* Values are given for Weld Neck (WN) flange type. For other types (Slip-On, Blind, etc.) please contact us.
Pressure Classes & Flange Types
Pressure Classes (ASME)
* Actual working pressure varies based on material and temperature.
PN Ratings (EN 1092-1)
* PN: Nominal Pressure - maximum working pressure at 20C reference temperature (bar).
Common Flange Types
Weld Neck (WN)
Butt-welded to pipe. Ideal for high pressure and temperature.
Slip-On (SO)
Slides over the pipe and is welded. Easy installation, for low pressure.
Blind (BL)
Used to close pipe ends. Has no bore opening.
Socket Weld (SW)
For small-bore pipes. Pipe is inserted into the socket and welded.
Threaded (TH)
Threaded connection. Ideal for environments where welding is not possible.
Lap Joint (LJ)
Used with stub end. Preferred in frequently disassembled lines.
Need Flanges?
Contact us for flange supply in all pressure classes per ASME B16.5 and EN 1092-1 standards.
How are flange dimensions standardized?
Flange dimensions follow two main systems: EN 1092-1 in Europe (PN pressure rating + DN nominal diameter) and ASME B16.5 in North America (Class + NPS). A flange's key dimensions are outside diameter (OD), bolt circle diameter (PCD), number/size of bolts and thickness. Example: DN100 PN16 → OD 220 mm, PCD 180 mm, 8 × M16 bolts.
PN/DN vs Class/NPS systems
DN (Diameter Nominal) is the nominal pipe size; PN (Pressure Nominal) is the pressure rating (PN6, PN10, PN16, PN25, PN40...). On the ASME side, NPS is the nominal size in inches and Class is the pressure-temperature rating (150, 300, 600...). The two systems are NOT identical: PN16 ≈ Class 150 is only an approximate equivalent and the bolt patterns differ. For a proper seal, the flange, gasket and mating flange must share the same standard and rating. The point most often confused in steel flange dimensions is the relationship between PN10 and PN16. From DN15 up to DN50 the connecting dimensions of the two ratings are identical — at DN50 both use a 165 mm outside diameter, a 125 mm bolt circle and 4 × M16 bolts, so the flanges physically bolt together. They diverge from DN65–DN80 onwards: at DN80 a PN10 flange is 185/145 mm while PN16 is 200/160 mm, and the bolt circles no longer line up. The habit picked up on small sizes — "PN10 and PN16 are the same" — therefore turns into a wrong order on large ones; always write DN and PN together. A flange size is not a single number. Three dimensions define the connection: outside diameter (D), bolt circle diameter (K or PCD) and bolt count/size — these are fixed by the standard. Flange thickness (b) varies with the flange type: weld neck (Type 11), slip-on (Type 01) and blind (Type 05) can differ at the same DN/PN. The sealing face (RF, FF, RTJ) and the gasket choice are part of the order information too.
PN16 steel flange dimension chart (EN 1092-1)
| DN | Outside Ø D (mm) | Bolt circle K (mm) | Bolts | Thickness b (mm) |
|---|---|---|---|---|
| DN15 | 95 | 65 | 4 × M12 | 14 |
| DN25 | 115 | 85 | 4 × M12 | 16 |
| DN50 | 165 | 125 | 4 × M16 | 18 |
| DN80 | 200 | 160 | 8 × M16 | 22 |
| DN100 | 220 | 180 | 8 × M16 | 24 |
| DN150 | 285 | 240 | 8 × M20 | 26 |
| DN200 | 340 | 295 | 12 × M20 | 26 |
| DN250 | 405 | 355 | 12 × M24 | 28 |
| DN300 | 460 | 410 | 12 × M24 | 30 |
| DN400 | 580 | 525 | 16 × M27 | 32 |
Outside diameter, bolt circle and bolt pattern are fixed by EN 1092-1. Thickness (b) varies with flange type — weld neck (Type 11), slip-on (Type 01) and blind (Type 05) can differ at the same DN/PN; check the ordering standard for the exact value. Use the calculator above for other pressure classes (PN6, PN10, PN25, PN40) and ASME Class equivalents.
Frequently Asked Questions
What are the dimensions of a DN100 PN16 flange?+
Outside diameter 220 mm, bolt circle (PCD) 180 mm, 8 × M16 bolts (EN 1092-1).
What is the difference between PN and Class?+
PN is the European (EN) pressure rating in bar; Class is the ASME (US) pressure-temperature rating. PN16 ≈ Class 150 is an approximate equivalent, with different bolt patterns.
How many bolts does a flange have?+
It depends on size and rating: 4 for small DN, 8 for mid sizes, and 12–16+ for large flanges.
What do flange face types (RF, FF, RTJ) mean?+
RF (raised face) is most common, FF (flat face) suits low pressure/cast bodies, and RTJ (ring type joint) is used for high pressure.
What are the dimensions of a DN200 PN16 flange?+
Outside diameter 340 mm, bolt circle 295 mm, 12 × M20 bolts (EN 1092-1). The PN10 flange of the same size is 335/295 mm with 8 × M20 — the bolt count differs, so the two cannot be swapped.
Do PN10 and PN16 flanges fit together?+
From DN15 to DN50 the connecting dimensions are identical, so they do fit. From DN80 upwards they diverge (DN80: PN10 185/145 mm, PN16 200/160 mm) and no longer match. Always state DN and PN together when ordering.
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