Engineering reference · ASME B16.5
ASME B16.5 Pressure-Temperature Rating Calculator
Pick the flange material, the pressure class and your design temperature. The calculator reads the rating from the ASME B16.5-2025 table for that material group and interpolates between its temperature rows, as the standard permits.
Rating
| Temperature | Class 150 | Class 300 | Class 400 | Class 600 | Class 900 | Class 1500 | Class 2500 |
|---|---|---|---|---|---|---|---|
| Min. to 38 °CMin. to 100 °F | 19.6 | 51.0 | 68.0 | 102.0 | 153.1 | 255.1 | 425.1 |
| 50 °C122 °F | 19.1 | 49.8 | 66.4 | 99.6 | 149.3 | 248.9 | 414.9 |
| 100 °C212 °F | 17.7 | 46.7 | 62.3 | 93.4 | 140.1 | 233.5 | 389.1 |
| 150 °C302 °F | 15.8 | 45.1 | 60.1 | 90.1 | 135.2 | 225.3 | 375.4 |
| 200 °C392 °F | 13.8 | 43.8 | 58.4 | 87.6 | 131.5 | 219.1 | 365.1 |
| 250 °C482 °F | 12.1 | 42.0 | 56.0 | 83.9 | 125.9 | 209.8 | 349.7 |
| 300 °C572 °F | 10.2 | 39.9 | 53.2 | 79.8 | 119.7 | 199.5 | 332.6 |
| 325 °C617 °F | 9.3 | 38.7 | 51.6 | 77.3 | 116.0 | 193.4 | 322.3 |
| 350 °C662 °F | 8.4 | 37.6 | 50.2 | 75.3 | 112.9 | 188.2 | 313.7 |
| 375 °C707 °F | 7.4 | 36.4 | 48.5 | 72.8 | 109.2 | 182.1 | 303.4 |
| 400 °C752 °F | 6.5 | 34.6 | 46.2 | 69.3 | 103.9 | 173.1 | 288.6 |
| 425 °C797 °F | 5.5 | 28.7 | 38.3 | 57.5 | 86.2 | 143.7 | 239.4 |
| 450 °C842 °F | 4.6 | 23.0 | 30.6 | 45.9 | 68.9 | 114.9 | 191.4 |
| 475 °C887 °F | 3.7 | 17.5 | 23.3 | 35.0 | 52.5 | 87.4 | 145.7 |
| 500 °C932 °F | 2.8 | 11.5 | 15.4 | 23.0 | 34.6 | 57.6 | 96.0 |
| 538 °C1000 °F | 1.4 | 5.8 | 7.7 | 11.6 | 17.4 | 29.0 | 48.4 |
Maximum working gauge pressure at each temperature, ASME B16.5-2025 Table 2-1.1 (bar at °C rows).
What the rating is. An ASME B16.5 rating is the maximum allowable working gauge pressure for the flange at that temperature, set by its material group and class. It does not cover the bolting, gasket or piping beyond the flange; a joint of two different flanges takes the lower rating. Interpolating between temperature rows is permitted, which is what this calculator does. Interpolating between classes is not.
Below 38 °C. Each table starts at "Min. to 38 °C (100 °F)": the rating does not rise below 38 °C. The 2025 edition no longer prints −29 °C as the lower limit. How cold a flange may be used is set by the code that references the standard, such as the ASME B31 piping codes and ASME B31T, and depends on the material, its thickness and impact testing. Appendix G gives examples: A105 and A216 WCB −29 °C (−20 °F) without impact testing; A350 LF2 Cl. 2 −46 °C (−50 °F), impact tested; F304H and F316H −198 °C (−325 °F); F304, F316, F304L, F316L, CF8 and CF8M −254 °C (−425 °F). Low-temperature requirements must reach the manufacturer before purchase.
Test pressures. Flanges are not required to be pressure tested by the manufacturer; they are tested with the system when the code calls for it, at up to 1.6 × the 38 °C rating. Flanged fittings get a shell test of at least 1.5 × that rating, rounded up to the next 1 bar (25 psi).
Units. bar and MPa come from the standard's SI tables (bar at °C rows); psig comes from its U.S. customary tables (psig at °F rows). The two are calculated separately, so a converted value can differ slightly: group 1.1 Class 300 is 51.0 bar and 740 psig (51.02 bar). Interpolated values are rounded down.
Material groups on this page. Group 1.1 (A105, A350 LF2, A216 WCB), group 2.1 (F304, F304H, CF8), group 2.2 (F316, F316H, CF8M) and group 2.3 (F304L, F316L). The 2025 edition changed several ratings. Group 1.1 Class 300 at 850 °F is now 320 psig, against 270 psig in earlier editions, and its 38 °C metric rating is now 51.0 bar, against 51.1 bar. Many published charts still print the older values.
Reference only. This page is a buying aid compiled by BLD Forge Direct from ASME B16.5-2025. It is not the standard. Design and acceptance follow the edition of ASME B16.5 named in your specification.
Ratings checked 2026-10-12 · ASME B16.5-2025 Tables 2-1.1, 2-2.1, 2-2.2 and 2-2.3 with their U.S. customary (C) tables · Classes 150 to 2500.