Pressure Vessel Wall Thickness Calculator
This calculator determines the minimum required wall thickness for a cylindrical pressure vessel shell using the ASME Boiler and Pressure Vessel Code (BPVC) Section VIII Division 1, formula UG-27(c)(1). Enter the internal design pressure, inside radius of the cylinder, allowable stress for your material at design temperature (from ASME Section II Part D), weld joint efficiency, and any corrosion allowance. The result is the minimum calculated thickness plus corrosion allowance. This is an educational tool; final design must be reviewed by a registered professional engineer and comply with the applicable edition of ASME BPVC.
ASME UG-27 cylindrical shell formula
t = P × R / (S × E - 0.6 × P)
Total t = t + CA
MAWP = S × E × t / (R + 0.6 × t)
Where: P = design pressure (MPa), R = inside radius (mm), S = allowable stress (MPa) per ASME Section II Part D, E = joint efficiency (0.65 to 1.0), CA = corrosion allowance (mm).
The formula applies when t does not exceed 0.5 * R or P does not exceed 0.385 * S * E. For thicker shells, use the alternative formula in ASME UG-27(c)(2).
Design considerations
- Always round up the calculated thickness to the next available plate thickness from your supplier.
- Include a minimum corrosion allowance per your process fluid corrosivity and service life.
- Nozzle reinforcement, support saddle loads, and wind/seismic loads are not included here and require separate calculations.
- Hydrostatic test pressure is typically 1.3 times the MAWP per ASME UG-99.
Pressure vessel calculator: frequently asked questions
What formula does ASME use for pressure vessel wall thickness?
ASME BPVC Section VIII Division 1, UG-27 gives the minimum thickness as: t = P * R / (S * E - 0.6 * P), where P is design pressure (psi or MPa), R is inside radius, S is allowable stress, and E is the weld joint efficiency (0.65 to 1.0).
What is joint efficiency (E) in pressure vessel design?
Joint efficiency E reflects the quality of the welded seam. ASME assigns E = 1.0 for full radiographic examination, E = 0.85 for spot radiography, and E = 0.70 for no radiography. A lower E means a thicker wall is required for the same pressure and material.
What is corrosion allowance and why is it added?
Corrosion allowance (CA) is extra wall thickness added to compensate for material loss over the vessel's service life. Typical CA values are 1.5 mm to 3.0 mm for carbon steel in mild service and up to 6 mm for more corrosive environments. The total minimum thickness shipped = calculated t + CA.
What are typical allowable stress values for carbon steel?
ASME Section II Part D lists allowable stress values. For SA-516 Grade 70 carbon steel at 100 degrees C, S is approximately 138 MPa (20,000 psi). Always use the current edition of ASME Section II Part D for your specific material and temperature.
Does this calculator apply to spherical heads?
No. This calculator uses the cylindrical shell formula from ASME UG-27(c). For hemispherical heads, the formula is t = P * R / (2 * S * E - 0.2 * P). For 2:1 ellipsoidal heads, t = P * D / (2 * S * E - 0.2 * P). Use the appropriate formula for each component.
Official sources
- ASME Boiler and Pressure Vessel Code Section VIII Division 1, UG-27: ASME BPVC Section VIII.
- ASME Section II Part D (Materials Properties): ASME Section II Part D.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.