ANSI vs PN/DIN Flange Dimensions Explained
This free flange dimension calculator covers the two flange standards engineers most often need to compare: ANSI/ASME B16.5 (imperial, Class 150 and 300) and PN/DIN to EN 1092-1 (metric, PN 10, 16 and 40). Select a size and rating to see the outside diameter, bolt circle diameter (BCD), bolt count, bolt size, hole diameter and flange thickness — then use the built-in cross-reference to check whether an ANSI flange and its nearest PN equivalent will actually bolt together.
Why ANSI and PN flanges are not interchangeable
ANSI and PN flanges follow different design rules, so even when the nominal size and bolt count look similar, the outside diameter and bolt circle usually differ. The classic example is a 4-inch ANSI Class 150 flange versus a DN100 PN16 flange: both use 8 bolts, but their outside diameters and bolt circles differ by roughly 9–10 mm — so they will not mate without an adaptor flange. Mismatched flanges lead to misaligned bolt holes, poor gasket seating, leaks and potential failure under pressure, which is exactly what this tool helps you avoid.
How to identify a flange
Measure the flange outside diameter (OD), the bolt circle diameter (BCD) between opposite bolt-hole centres, and the number and size of the bolt holes. Match those three figures against the dimension tables for ANSI/ASME B16.5 and EN 1092-1 to find the standard, nominal size and pressure class. Bolt circle and bolt-hole count are the fastest checks — get those wrong and the flange simply won't bolt up.
Browse Flanged Valves
All valves below are available with flanged ends to ANSI/ASME B16.5 or PN/DIN EN 1092-1. Use the dimension tool above to confirm the correct OD, bolt circle and bolt count before ordering.
- Ball Valves — full-bore and reduced-bore, ANSI Class 150/300 flanged ends as standard on larger sizes
- Butterfly Valves — wafer, lug and double-flanged body styles; confirm flange OD and bolt circle before specifying
- Gate & Globe Valves — raised face flanged ends to ASME B16.5; flange thickness and BCD critical for pipe mating
- Check Valves — flanged swing and piston check valves; OD and bolt circle must match the adjacent flanges in the line
- Actuated Ball Valves — complete automated packages with flanged bodies; use the lookup to verify the flange spec before ordering
Flange Dimension FAQs
Will ANSI and PN flanges bolt together?
Generally no. ANSI/ASME and PN/DIN are different standards with different outside diameters, bolt circle diameters and bolt-hole patterns, so they usually will not bolt together directly — even at a similar nominal size and bolt count. For example, a 4-inch ANSI Class 150 and a DN100 PN16 both have 8 bolts, but the OD and bolt circle differ by around 9–10 mm. Use an adaptor or transition flange, and always confirm OD, BCD and bolt holes before assembly.
What is the PN equivalent of ANSI Class 150?
PN16 is the closest nominal pressure equivalent to ANSI Class 150 (Class 150 ≈ 20 bar at 38°C; PN16 = 16 bar at reference temperature). But equivalent does not mean interchangeable — the physical dimensions still differ, so the flanges won't necessarily bolt together.
What is bolt circle diameter (BCD) on a flange?
Bolt circle diameter (BCD), also called pitch circle diameter (PCD), is the diameter of the imaginary circle through the centre of every bolt hole. For two flanges to mate, their BCD, bolt count and bolt-hole size must all match. It's one of the most important dimensions to verify before ordering a mating flange.
How do I identify what flange I have?
Measure three things: the outside diameter (OD), the bolt circle diameter (BCD) between opposite bolt-hole centres, and the number and size of the bolt holes. Compare against ANSI/ASME B16.5 and EN 1092-1 tables to find the matching standard, size and pressure class.
Is DN100 the same as 4 inch?
DN100 is the nominal metric equivalent of a 4-inch pipe size, but a DN100 PN flange and a 4-inch ANSI flange are not dimensionally identical. The bolt circles and outside diameters differ, so although they describe a similar bore they are not interchangeable as flanges.
What is the difference between PN10, PN16 and PN40?
PN means Pressure Nominal — the approximate pressure rating in bar at reference temperature. PN10 ≈ 10 bar, PN16 ≈ 16 bar, PN40 ≈ 40 bar. Higher ratings use larger or more numerous bolts and thicker flanges. Smaller sizes often share the same drilling across PN10 and PN16, but this diverges at larger sizes and higher ratings.
