Free engineerin' tool
Flange Identifier: Size and Class From Your Measurements
Got a flange with no markin's you can read? Measure four things: the outside diameter, the bolt circle (center of one hole to the center of the hole straight across), the number of bolt holes and the bolt hole diameter. This identifier checks 'em against ever' ASME B16.5 size and class (1/2 to 24 inch, Class 150 to 2500) and ASME B16.47 Series A and B (26 to 60 inch) on the Texas Flange flange dimension tables, and ranks the closest matches. The bolt circle and hole count matter most. Only got the spacin' between two neighborin' holes? Turn it into a bolt circle with the bolt circle calculator.
Edge to edge, across the widest part.
Center of one hole to the center of the hole straight across from it.
Only got the spacin' between two neighborin' holes? Turn it into a bolt circle
This here's a reference tool for plannin' and quotin'. Check it against your purchase spec and your site's procedures before y'all go usin' it.
Get y'all a flange quote
Questions Folks Ask Us
How do y'all measure a flange size?
Measure the outside diameter, the bolt circle diameter (center of one bolt hole to the center of the hole straight across), the number of bolt holes and the bolt hole diameter. The bolt circle and hole count tell you the size and pressure class a whole lot better than the outside diameter by itself.
Is the flange size the same as the outside diameter?
Nope. The nominal size (NPS) is about the pipe the flange fits. A 4 inch Class 150 flange, say, has a 9 inch outside diameter and a 7-1/2 inch bolt circle with eight 3/4 inch holes.
How come some results show two classes?
Some sizes share the same outside diameter and drillin' in two classes. On ASME B16.5, for instance, Class 300, 400 and 600 share the same O.D. and drillin' at 1/2 inch, and Class 900 is the same as Class 1500 from 1/2 to 2-1/2 inch. Check the markin's or hub, or go with the higher class.
How do I measure the bolt circle on a flange with an odd number of holes?
Measure the center-to-center spacin' between two neighborin' holes and divide by sin(180 / number of holes), or put the spacin' in the Texas Flange bolt circle calculator.
What if my flange don't match any ASME size?
It might be built to another standard, like AWWA, MSS SP-44, EN 1092-1 (DIN) or JIS, or it might be custom-drilled. Send your measurements to Texas Flange and we'll help y'all find a match.
