Pipe Wall Thickness Calculator
Calculate the minimum required pipe wall thickness based on internal design pressure using the ASME B31.3 Process Piping formula.
Formula — ASME B31.3 Clause 304.1.2
Pressure design thickness:
t = (P × D) / (2 × (S × E + P × Y))
Minimum ordered thickness (accounting for corrosion and mill tolerance):
tordered = (t + c) / (1 − mill% / 100)
Where:
- P — Internal design pressure (MPa)
- D — Outside diameter of pipe (mm)
- S — Allowable stress for pipe material at design temperature (MPa)
- E — Longitudinal weld quality factor (0.80–1.0)
- Y — Temperature-dependent coefficient (0.4–0.7)
- c — Sum of mechanical allowances including corrosion (mm)
- mill% — Manufacturer's mill undertolerance on wall thickness (%)
Assumptions & References
- Formula applies to straight pipe under internal pressure only (thin-wall assumption: t < D/2).
- Based on ASME B31.3-2022 Process Piping, Clause 304.1.2.
- Default mill tolerance of 12.5% applies to most seamless and ERW carbon steel pipe per ASTM A106 / A53.
- Allowable stress values (S) should be taken from ASME B31.3 Appendix A tables at the design temperature.
- Y coefficient values are per ASME B31.3 Table 304.1.1; Y = 0.4 is conservative for most carbon steel below 482°C.
- Does not account for external pressure, bending loads, thermal expansion, or branch reinforcement — additional checks required per code.
- Results should be verified by a qualified engineer before use in any design or construction activity.