Flange dimensions: EN 1092-1 PN6 to PN40 and ASME B16.5 Class 150 and 300

Flange dimension tables for EN 1092-1 PN6, PN10, PN16, PN25 and PN40 and ASME B16.5 Class 150 and 300: outside diameter, bolt circle, number and size of bolts, and why PN and Class flanges do not mate.

Updated October 17, 2026

Two flanges bolt together only when their connection dimensions match: the outside diameter, the bolt circle and the number and size of the bolt holes. In Europe these are set by EN 1092-1 for each nominal size (DN) and pressure rating (PN); in the US by ASME B16.5 for each pipe size (NPS) and pressure class. The tables below give the connection dimensions for the ratings used most.

How to read the tables

• D — flange outside diameter.
• k — bolt circle diameter, through the centres of the bolt holes.
• Bolts — number of holes × bolt thread. The hole is a few millimetres larger than the bolt.
• Pipe OD — outside diameter of the steel pipe the flange is welded to, from EN 10220 series 1.
• Connection dimensions are the same for every flange type of one rating: a PN16 weld neck, slip-on, plate and blind flange of the same DN bolt to each other. Thickness, hub and weight differ by type.

EN 1092-1 PN16 flange dimensions

EN 1092-1 PN10 from DN200

Up to DN150, PN10 flanges use the PN16 dimensions above. From DN200 the two ratings differ, so a PN10 and a PN16 flange of the same size no longer mate.

EN 1092-1 PN25 and PN40

Up to DN80, PN16, PN25 and PN40 flanges share the same connection dimensions. From DN100, PN25 and PN40 have a larger outside diameter, bolt circle and bolt size. A PN40 flange is thicker than a PN16 flange even where the bolt pattern is the same.

EN 1092-1 PN6

PN6 flanges are smaller than PN10 and PN16 at every size and do not mate with them. They are used for low-pressure water, air and ventilation lines.

ASME B16.5 Class 150 flange dimensions

ASME B16.5 Class 300 flange dimensions

Do PN16 and Class 150 flanges fit together?

In general, no. At DN50 a PN16 flange has a 125 mm bolt circle and M16 bolts, while a 2" Class 150 flange has a 120.7 mm bolt circle and ⅝" bolts. The holes do not line up, the bolt threads differ, and European pipe and ASME pipe also differ in outside diameter at several sizes, such as DN65 (76.1 mm against 73.0 mm). Order flanges in the system of the equipment they connect to, or use an adapter flange drilled to both patterns.

Flange types in EN 1092-1

• Type 01 — plate flange — a flat ring slipped over the pipe and fillet-welded. Simple and economical for low pressures.
• Type 05 — blind flange — a solid plate that closes the end of a pipe or nozzle.
• Type 11 — weld neck flange — a tapered hub butt-welded to the pipe. The best choice for high pressure, temperature changes and cyclic loads.
• Type 12 — slip-on flange with hub — slipped over the pipe and welded inside and out; the ASME equivalent is the slip-on flange.
• Type 13 — threaded flange — screwed onto threaded pipe without welding, for small sizes and low pressures.
• Facing — A is a flat face, B1 a raised face. Raised faces concentrate the gasket load; a flat-face flange should be bolted only to another flat face.

Flanges we supply

• Carbon steel to EN 1092-1 — weld neck, plate, blind and threaded flanges.
• Slip-on flanges — carbon steel, stainless steel 304 and stainless steel 316.
• Stainless steel 304 — weld neck, plate and blind flanges.
• Bolting — flange bolts in class 8.8 and flange nuts. For pipe sizes and walls see the pipe schedule chart.

Frequently asked questions

Send your flange list with type, DN or NPS, rating, facing and material in a quote request. EN 10204 3.1 certificates are available on request.