ASME B16.5 Flange Rating Calculator
Look up the allowable working pressure for a flange class at a given design temperature, interpolated between standard rating-table points, for two of the most common ASME B16.5 material groups.
Rating Lookup
How the lookup works
ASME B16.5 itself uses linear interpolation between listed temperature points and does not permit extrapolation beyond the table — this calculator follows the same convention and will flag values outside the tabulated range.
Reference table — typical ratings, psig (rating at upper temperature bound of range)
| Temp, °F | 150 | 300 | 600 | 900 | 1500 | 2500 |
|---|
Table shown reflects the material group currently selected above.
Frequently asked questions
Why does allowable pressure drop as temperature rises?
Material yield and tensile strength both decrease with temperature, so the same flange class supports less internal pressure at higher design temperature. This is why the rating is always expressed as a pressure-temperature pair, not a single pressure number.
What's the difference between Group 1.1 and Group 2.1?
Group 1.1 covers common carbon and low-alloy steel forgings and castings (A105, A216 WCB) used in general hydrocarbon and utility service. Group 2.1 covers austenitic stainless steels (304/304L family) used where corrosion resistance is required. Different material groups have different rating curves even for the identical flange class and dimensions.
Can I use this instead of the actual ASME B16.5 standard?
No. This is a preliminary estimating tool. Final flange class selection for procurement, fabrication or code-stamped documentation must reference the current purchased edition of ASME B16.5 Table 2, the exact material specification and grade (not just the material group), and any project-specific derating.
Does this account for gasket or bolting limits?
No — this is the flange body pressure-temperature rating only. Gasket seating and bolt load are separate checks; see the Flange Bolt Torque Calculator for Wm1/Wm2 gasket and bolt-load verification on a specific flange.